I know that there are countless threads already on this, but even after trying all those suggestions I still can't seem to resolve the issue.

I was installing BitDefender and had to restart the computer. The computer would boot up and seem to be loading Windows, but then it just goes blank, and the keyboard and the mouse don't seem to be getting power either.

I've tried booting into the last good known configuration and that does the same thing as above.
Booting into Safe Mode gives me the BSOD:
STOP: c000021a (Fatal System Error)
The Windows Logon Process System process terminated unexpectedly with a status of 0xc00000139 (0x0000000 0x00000000). The system has been shut down.

I've tried to repair Windows XP..but the computer won't boot from the CD..and I've checked the BIOS and that all seems to be fine It's setup to book from CD-ROM first, but it's not..

I don't know what else to do and would appreciate any help I could get.

Hi,
First up try resetting the BIOS by removing the motherboard battery for a few minutes then replace, reset the BIOS to CD first boot and try again.
If that will not work, please post more information about your PC

Okay, I've tried that and it still won't boot from CD.
It is an older Gateway LP Mini Tower TB Essential 500
Pentium III
Processor Speed 500 MHz
Front Side Bus 100 MHz
Cache RAM 512 KB
System Memory 320 MB
Hard Drive 19 GB
NVIDIA Vanta/Vanta LT Video Card
Creative Sound Blaster with Line In/Out/Mic

Hi, P3.. it is not worth trying to boot anyway.
Sorry I can not help you.

I know it's not worth it, but is there any way of getting it to boot without having any expenses?

Hi,
I was serious when I said I can not help you, I have no idea how to fix it, but the only way I would boot it is with a size 10 boot.

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