Hi! If I'm understanding you; you can't boot from a live CD or the HD?? If you are sure your HD is good and you reseated the RAM, you could try memtest86. There are ways to test the PSU. I have a meter I use. I don't know a way to test MB. PSU meters are very cheap 10$. I have a Rosewell that I use.
PS memtest86 is a live CD. You might also want to try seatools dos also. You can Google both. If you need a link, I can get you one. WD also has a dos ISO. Sounds like a hardware problem and now, that's finding which one is causing this. You could always go with Linux :smileyhappy: If you can boot Linux, IMHO you eliminate a lot of hardware causes.
PS It sounds like you know what you're doing, so let me know about Puppy Love!! If you have hardware problems, recovery media is not much help.:smileywink: I forgot to mention that I'm very old and very windy,but I try very hard to help.
Dokie!
http://puppylinux.org/main/Overview%20and%20Getting%20Started.htm
You don't need a HD to boot Puppy Love.:smileywink: