Screen goes black on or after welcome screen

Although people do it, its best to post your own thread, especially when the thread is already huge like this one. It only confuses people. Im only telling you so you will get better and more answers to your own problem. So if i could talk you into starting your own, i will go there and try and help you.
Your issues are actually likely different enough anyway.
Getting to your issue, i am sorry to have to tell you that brown-outs (low or no power) are even worse than power surges (too much extra power). In truth the electrical systems out there were never made with the needs of computers, which needs are above everday items around the house.
That is why brown-outs and surges are known to kill motherboards, hard drives, video cards, power supplies, etc. I live in an area of my city with known poor power. Nobody told me so i lost mobos, hard drives, etc, until i installed a UPS (uninterruptible power suppy). In these 5 yrs i have lost absolutely NOTHING.
And a power supply could still be bad and still power up your pc!
I reckon you have been nailed bad and i hope you are wrong, but i will try and help you, just start your own thread. For one thing, you need to list all your system specs, what add-ons you may have, etc.
For instance, do you have a video card or is it built in video? If its a separate card i would suggest you try another video card. But since i dont know all the specs on your pc, this is only an educated guess at best. And try another monitor as well, actually i would do that first of all, then the vid card if you have a vid card.
I suspect something got fried, so when you get your system going again, please buy yourself a UPS. You dont have to get the best, even the cheapest will work. I need a whole page to explain why but trust me, a cheap one will do.
Getting back to your immediate issues, do everyone a favor and post your own thread. We can help you better that way. And would you have any warranties on your pc or some or all of its parts. Certain hard drives have a 3 yr warranty, others only a year.

i opened the command prompt yesterday and typed in fixmbr but it didn't recognise it. i typed in help to see what other commands i could put in but i couldn't really see any that would help me. should i just try writing it again booting from the cd? oh yah, i've also uninstalled avg and downloaded the latest version.

isnt fixmbr a recovery console command?

N3051M, you are right, i gave the wrong instructions. I was trying to think of an easy way , turns out to be harder, lol.

To fix the mbr, and it must be fixed before anything else is done, you can use the recovery console or do it using a win98 boot disk.

From this trusty website:
http://www.ntfs.com/mbr-damaged.htm

You will find this:

The simplest way to repair or re-create MBR is to run Microsoft's standard utility called FDISK with a parameter /MBR, like

A:\> FDISK.EXE /MBR

FDISK is a standard utility included in MS-DOS, Windows 95, 98, ME.

If you have Windows NT / 2000 / XP, you can boot from startup floppy disks or CD-ROM, choose repair option during setup, and run Recovery Console. When you are logged on, you can run FIXMBR command to fix MBR.

I just use a win98 boot disk, even in win xp. Set bios to boot from floppy and use win 98 boot disk. Use the same fdisk command.

What i should have said originally was to boot up using a windows 98 boot disk and typed "fdisk /mbr" , without the quotes.

That is the correct procedure, although you can also do it using the win xp recovery console. I only use the win 98 boot floppy because that is what i have done for years, just temporarily forgot the right command, lol.

i've finally just gotten round to writing the MBR again.
i did it once but then the pc reset a couple of times, so i decided to do it again.
it started fine this time and i've reinstalled avg and started a scan and it's read the MBR section as ok
hopefully this'll be the end of the problem but if anything comes up or if it gets up to it's old tricks again, i'll let you know! :grinthumb

So you have now repaired your master boot record (mbr), which is where some of the worst virus and trojans are placed.

And your system is up and running fine?

In addition to running AVG can i suggest you go to trend-micro and run their free scan. They catch more than AVG or any other a\virus prog will catch as a\virus are very poor in finding trojans, which is likely what you had in your mbr! Trend-micro will install a small prog that wont hurt your pc and it will do a complete scan and get rid of any trojans you may still have on your pc.
I have done well over 100 scans on many different pcs and never a problem.
And do let us know how you end up.

ok, well when this scan finishes then i'll use that.
i've used it before but i don't think it found anything.
although it was a long time ago...
oh yeah, and because it only take about 20 mins i was going to do a spyware scan with spybot after as well, just to see.

Good idea for you to run any good type of a\virus or malware\trojan prog.
Let us know the results. Glad your pc is running better now.
Those darn trojans can really mess up a pc and most a\virus cant catch them or fix them!

avg didn't find anything and the trend micro housecall found and removed a couple of spyware things, but no trojans.
when i start my pc though it seems to be resetting the first time and being ok the second time. i haven't got any other problems apart from a bit of slowness but it's just windows media player and firefox. probably all the extensions and plugins i have!
the housecall scan found oe thing that it couldn't get rid of but i think it was some spyware, i can't remember the name because it was just a few random letters and stuff, but ended with 69. there were also a couple of vairants with the same name but ending with (i think) 70 and 71. i did a scan with spybot as well which found one spyware and i removed that too.
lots of scans with stuff removed, but i'll do a full scan with ad-aware later.
oh yeah, avg is saying that the mbr is ok, and i keep meaning to get the memtest software but i just need to remember! hopefully i'll remember when i get home.

Thanks for the reply.

Are there any red or yellow markings in device mgr?

Let us know the result of the ram test.

Here is memtest:
http://www.memtest86.com/

Dont forget, you have to test only one stick of ram at a time or it wont work right.

i've downloaded memtest and i'll have to run it next time i turn my computer on, which will be tomorrow.
i looked through all the sections of device manager and there aren't any yellow or red things.

If all is well with your memory after you run each stick thru memtest then i have an idea that may help find the problem, so let us know right away what memtest has to say. One stick at a time, sorry, but i want to make sure you remember, lol.

i have memtest running at the moment, and i think it's going ok. it's on the first stick and says 0 under errors, but we'll wait and see. it'sdone 5 "Pass" things so far, and it's been running for just over an hour. i had a bit of a wake-up call today when i tried to tun my pc on and it reset itself loads of times. i'm not sure how many times it did it, because i wasn't in the room, but when i went back, i ended up sending 17 error reports. it could be a couple more though because i don't think they all brought up the microsoft website. they mostly said that they have no idea what the problem is, but some of them said that it was because i don't have the latest video driver, even though i do. i've tried what it said to do on there before as well and it doesn't make any difference, installed the new driver and lowered the acceleration (like it says) but it did no good.
i'm going to let memtest test my ram, i just hope that it doesn't take all day!
oh, and also (if any reads this soon) does memtest just get to the end of it's process on its own or do i have to stop it?

are you doing memtest in dos mode (boot up the pc with memtest) or inside windows? are you testing 1 stick at a time?

sorry.. i kinda lost track of whats happening on this thread...

i burned the iso file onto a cd and i've booted from it, i'm using another computer to do this. yeah, i've taken one of the sticks out (i only have 2) so i'll put the other one in when it finishes with this one.

I usually wait til its done anywhere from 6 to 10 passes. If there arent any errors then the ram is likely ok.

ok, i expect it's done 10 by now so i'll stop it and do the other stick.

i've now run memtest on both ram sticks, and it didn't find any problems. after i exited memtest i forgot to turn the pc off and put the oter ram stick back in, so i tried starting it up with just one stick at a time, but it reset both times. i then took out a sound card that i'm not using and disconnected a usb 2.0 thing that i also don't use, but forgot to plug the cd input thing back into the motherboard for the built in sounds card (had a bit of a forgetful day really ) it started ok, and sent an error report, but when i typed another web address in, it reset as soon as i pressed enter. so i turned the pc off and plugged the cd input back in. it started alright again, but reset as i was screwing the other side of my case back on. i don't know if it could have been anything to do with me leaning on the case so that i could see the back, but i don't know. i did have the usb 2 thing plugged back in again too but now i've unplugged it again and everything seems quite good. if it keeps going ok then i'll put the side of the case back on again.
oh, and after sending 2 error reports since i've had the pc on this time, both of them are insisting that it's a video driver problem. i don't know if it's a conflict or wat, but i've already done what microsoft have told me to do.
i'm just going round in circles really, i suppose

just an update:
i now don't think that the usb thing had anything to do with it, because my pc started resetting again when i turned it on this morning.
i thought that the usb thing could have contributed because it's a usb 2 device but it only runs at usb 1.1 speed because my mobo is too old for usb 2.
oh well, i suppose you can basically ignore the last post apart from the bit where i said that i ran memtest and they came up ok. i still have the usb and the sound card disconnected though.
oh, and also if you want a picture of my psu (to see whet make it is etc...) i now have one that i can put up.

---31/05---
zone alarm was doing a virus scan yesterday and it found one virus. the pc's starting up better now, and it's working quite well so maybe that could have had something to do with it.