For some reason my PC (Dell Dimension 8300) suddenly won't boot.

When I power on I get the BIOS splash screen and then it goes to a black screen with flashing underscore and doesn't go any further.

If I try to reboot and enter BIOS (F2) it says entering BIOS then goes to black screen with flashing underscore

If I try to go to boot sequence (F8 or F12) it bleeps and then goes to black screen with flashing underscore

I have not made any recent (hardware or software) changes to the machine. I have had the machine several years and installed Windows 7 on it from Microsoft.com back in February - and its been quite happy all of this time.

If I put a new Windows 7 Install DVD in - unfortunately this is skipped due to previous setting in BIOS (HDD first)

Its running twin SATA drives - if I pull either of the HDD power leads or SATA leads it then says
>> SATA Primary/Secondary (as appropriate) drive 0 not found
It then sits on that message

The machine is running BIOS Dell A07

I have not moved the machine recently

I used the machine happily last night, shut-down normally. Then today got this problem when I turned it on

I am at a loss - it seems that I have a large paperweight at the moment

Thanks for your comprehensive condition of the error you are receiving

Try this:

Remove the secondary hard drive (by the way you only need to remove the Sata cable from the Motherboard end)
Also remove the data cable for your CD/DVD Drive (yes again from the motherboard end)

Then reseat your Windows system harddrive data and power cable
So presently you have your Windows drive only in your computer, fitted correctly

Then with the main power cord out, hold in your ON button for 30 secs (dispersing internal power)
Refit the power cable, and turn on

If you still have the issue, you may need to reseat your Ram, or even try another data or power cable to your Hard drive
By the way, the fault is your computer can not register the hard drive (or some other drive) connected to your computer, it will eventually time out, not that this matters. (it can also be faulty Ram, but less likely)

Many thanks for getting back so promptly - unfortunately I am still having problems...

First of all I unplugged both SATA data cables (from M/board) + DVD Drive data cable (from M/board). Then with mains lead unplugged, held in Power button for 30 secs.

Then plugged in 1x SATA data cable

Tried to boot up but received error various drive not present messages - neither could I enter BIOS

Swapped around SATA data cables, swapped around SATA power leads (the drives do spin)

Reseated the RAM

Power button (no mains) again for 30 seconds - still error messages and unable to enter BIOS.

Plugged both SATA drives in with except of DVD data - drive not present error message and unable to enter BIOS


Power button (no mains) again for 30 seconds - and plugged DVD data cable in. No error message but unable to enter BIOS and still hung booting

"Help" he cried plaintively...

Not entering Bios is not a big issue, as you can manually reset your Bios from the Motherboard
I recommend to read the manual on this, but generally its just a matter of removing the button battery (actually disperse power first) then locating the reset jumper (usually right next to the button battery, and then shorting two pins (obviously still with all power out)
The "pins" to short, are from you placing the tiny jumper over pins 2 and 3 or 1 and 2, (or whatever the manual says)
I tend to do it without the manual, as its usually stamped on the motherboard (in tiny writing)

There is another possibility (I know its never ending) It can be your Power Supply (even though it boots (kinda)
Before replacing/purchasing any parts through, I'd recommend blowing out all internal dust (especially in/through the power supply); with high compressed air