I am unsure if i am putting this in the right section but here goes anyway. I left my computer off for 4 weeks over the Christmas break and then when i got back it would not start and came up with a BSOD saying "Your Bios is not ACPI compliant" which is impossible. Then i turned it on the next day and it worked fine untill i turned it off again. Then when i came back and turned it on it all whirred up but no picture cam onto the screen. I can still blindly log into the computer as i have a logitech G15 keyboard which lets you know when you are on the login screen but the monitor just stays blank. The only way i have found to get it to work is to leave it on for 5-10 mins then turn it off and on again, which is very odd. I assume as it work perfectly after this that it is not a hardware problem but i am quite confused.

Some solutions that i have tried unsuccesfully:
-Checking monitor cables
-Removing, cleaning and reinserting the graphics card
-Removing and reinserting the RAM
-Checking hard drive and cd rom SATA/power cables
-Checking all cables plugged into the back of the computer

The only thing i can think of is that it needs to warm up but i don't see why or how to fix it???

Thanks for your help

You have failed to describe anything about the PC. Most important, how old is it? It could be old enough to need a new battery. You also do not say if when you 'turned it off' for 4 weeks, was that off as in the sense of Windows shut down, or off in the sense of switched off at the mains?

If all you need is a new battery, it is the round silver thing about 1cm diameter on the motherboard. Usually a CR2032 - about £2 from many big supermarkets because they also power certain mobile phones and similar.

The only problem you may hit is that taking the battery out whilst there is little or no charge in the motherboard capacitors may reset the bios, and you may need to put it back to what it should be (clue there was the APIC error - a motherboard can be configured APIC and often a few other things as well).

Try leaving the thing on and running for many hours, then reboot, get into the bios and note the current settings on each page before changing the battery.

my computer is two years old and the specs are
-Asus M2N32 WS Professional Motherboard
-AMD Athlon 64 x2 Dual core processor
-Nvidia GeForce 8800 GTS
-2GB RAM

When i said i left my computer off i meant that it was turned off at the mains

Sounds like a failing battery as gbhall suggested.
The BIOS may have already reset to defaults if they weren't set before. I'm guessing that everythings probably on "Auto" in the BIOS judging by your thread regarding RAM upgrade I'm advising you on.
Do as gbhall suggested to see if the battery will charge. Although under normal conditions a battery can go 6+ months without charge it will depend on the individual battery, and a failure after four weeks unpowered is indicative of the battery being on it's last legs and you could experience sporadic no POST's in future. Buying a new battery is probably the wisest course of action-changing it is a relatively simple task and is made even simpler if you have never had cause to change a BIOS option.

Ok i will try replacing the battery. If i have to reset the BIOS what are the main settings i need to change except for the RAM settings which i know about from "dividebyzero"
Thanks guys

Ok, now my system does not work at all. AAAAh!!! Now when i turn on my computer it whirs up but this time there is no picture on the screen and no lights on the keyboard or mouse. It happened just after i changed some settings in my bios for my RAM that "dividebyzero" told me about. I don't think it could have been anything i have done as i followed his instructions precisely. Then when i pressed F10 it restarted and then the screen just stayed black. I might just have to give in and take it to PCWorld
HELP!!!

First off reset the CMOS - one problem at a time.
IF you are using a new RAM kit
Remove power from the system.
Hit the power button to discharge the capacitors.
Move the CCMOS jumper to the clear position. (It's the CL_RTC 3-pin jumper next to the battery at the 7 o'clock postion-move the jumper block from the 1-2 pin position to the 2-3 pin position)
Remove the battery from the motherboard.
Go do something else for an hour.....
Replace the battery.
Place the jumper back in the normal position.
Restore power and boot up immediately into BIOS.
IF the BIOS does not load then power off and use just one RAM stick in the DIMM A1 (yellow slot closest to the CPU) slot and retry. If it still doesn't work then try the same
procedure using the 2nd stick- you may have a faulty RAM module. If the BIOS loads then...
Select "Load Optimized Defaults" and set the recommended voltage for your RAM
Save & exit.
On reboot, go directly into BIOS and set any other options you'd like to set (i.e. boot order, etc.).

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You were upgrading from 2x1Gb DR2-800 to 2x2Gb DDR2-800. Which kit did you end up getting (and its timings and voltage) ?
And I presume you're not using both the 2x1Gb and the 2x2Gb simultaneously.

I was not installing the new ram at the moment i was just changing the timing of my ram as i realised that the RAM i have at the moment was not set to the right speed and thats is when it all happened. Atm i have reset the cmos and the computer load up fine to the Bios but it is here i get stuck as i don't know what settings to change as it has bee a while since i set up my computers bios. when i save the settings there atm the computer loads up and then says "DISK BOOT FAILURE, INSERT SYSTEM DISK AND PRESS ENTER" Sorry for my stupidity!!!

There should be a menu bar at the bottom of the BIOS screen. Press F5 to reset to default.

Seems that your chipset doesn't allow for DDR2-800 operation without some tweaking
http://www.nforcershq.com/forum/m2n32-ws-pro-negative-experience-t67254.html
And the link that is provided in the third post
http://www.tomshardware.com/reviews/amd-reinvents,1258-9.html

Would suggest that the default speed should be DDR2-733.

oh ok i have reset it to defaults but i think the problem might be that it cant find an installed copy of windows. In the BIOS should there be an item in Primary IDE Master? how do i set the speed to DDR2-733, as the on;y choices i have are 400, 533, 667, 800 & 1066?

Yes, it should be set to the hard drive that your OS is installed on.

Once you're back up and running can you post back with the RAM setup that you have at the present time (i.e. are you running on 1 stick, or once you booted up ok then powered down and added the second stick) whether you are using the new kit or the old kit -and the details of the new kit if you're having problems with it.
I've got to head out- my folks across town have got computer troubles as well so I'm heading over. If you re-post and don't get an immediate response then that is why. Hopefully if you need a solution quickly then someone else on the forums can lend their brainpower to the cause.

ok well as it cant find my windows does that mean that i have to reinstall it? Or is there any way to find it. An OS reinstall would not be complicated as i have all my info backed up but it is so time consuming and i would prefer not to.
I am probably going to call it a night now as i have plans to go out, but i will post back tomorrow with updates and how i am getting on.
Thank you so much for all your help, i don't know how i would have coped without you!!!

The BIOS should detect the harddrive-if it has and the problem is that Windows can't initiate then I think your best bet would be to put your OS disc into the drive and select repair to correct the boot loader problem for the OS.
You would need to know the timings and voltage for your present RAM to set the values manually. All DDR2-800 RAM defaults to DDR2-667 at 5-5-5-15-2T @ 1.8volts as this is the JEDEC standard profile built into every module- If changing to DDR2-800 then the Command Ratealso needs to be set. Depending on the RAM in question these values may or may not change if setting to DDR2-800. This is an image from one of my systems-it shows (in the Memtest SPD program window) the varous profiles available for the RAM that are deemed stable for use in normal (non-overclocked) use:

JEDEC #0 DDR2-800 at loose 5-5-5-18 (2T) timings at 1.8v
JEDEC #1 DDR2-667 at loose 5-5-5-15 (2T) timings at 1.8v -this is normal default setting if the BIOS if let on Auto
JEDEC #2 DDR2-533 at standard 3-4-4-12 (2T) @ 1.8v
EPP #1 DDR2-800 performance setting 4-4-4-12-2T @ 2.0v -this is an nVidia chipset auto-detect standard setting.
EPP#2 DDR2-1000 performance setting 5-5-5-15-2T @ 2.0v -alternate nVidia chipset standard setting.
If you want to see all the profiles that RAM carries the you can download Memset here http://www.softpedia.com/get/System/System-Info/MemSet.shtml The RAM is guaranteed to run at the profiles listed-if it does not then the RAM is faulty (which can be tested easily enough) or the motherboard is the limiting factor- not likely on a reasonably high-end workstation board like yours.
As for the RAM speed selection you could try the auto select for DDR2-800 and leave all other values at Auto- the board will probably set values that it see's as optimum.
If this works fine then you can load CPU-Z (here http://www.cpuid.com/cpuz.php) and the utlilty will tell you the timings and voltage the board is using.
If this method doesn't work then post the details for the RAM kit you are using (and version number if it's Corsair) and I'll post step-by-step instructions -now that I have your motherboard manual

Ok well i left my computer for a few hours and now i have come back and when i try to boot from my OS disk it says "NTLDR is Missing" which did not happen before as i was able to load the OS disc with no trouble before. From what i have found online it says i need to boot from my os disc and go into the recovery console and copy two files http://www.computerhope.com/issues/ch000465.htm but all i get is "Access denied" so i can't copy the files. I hate that things keep going wrong!!!
I am using 2x1GB of ram atm as i have not ordered the new stuff yet. i have managed to set the ram as CL4 4-4-4-15 and it automatically sets it to DDR2-800 with a voltage of 2.0 and i think it is working fine.
Its just the stupid "NTLDR" thing now ARRRGGG!!!

Might pay to start another thread with the "Access Denied NTLDR Missing" tag. I'll go through MS's knowledge base and see if I can find the answer but I would suggest another thread start anyway because you may attract an answer from someone with first hand knowledge.
If you're back into the BIOS then once you get this problem out of the way then you can resurrect the RAM thread regarding the 4Gb upgrade. If I find out anything I'll post here or at the new thread if you start one.
Did you check the cables and select the USB keyboard option in your BIOS? (if you're using a USB kb that is)

ok i will make a new thread and post a link to it here. I don't think i have selected USB keyboard in my bios, where is the place i do that as i cant seem to find it
http://www.techspot.com/vb/topic141771.html#post843693

There doesn't seem to be an option in the BIOS for that, although if you can access the BIOS using a USB kb at the moment then it must be an auto-detect, so all good.

Well i did a full OS reinstall and it all works fine now, such a simple but tedious task!!!
Thanks for all your help