OUCH bro! Hey, why downgrade to build? You should be able to find a decent multi-core mobo and processor combo at New Egg or Tiger Direct for a decent price... depending on how much damage is done to your system and whether or not you are SATA or IDE, you also should be able to use parts from your current system too...
As for your TB hard drive.... how have you tested it? Have you put it in another system as a slave drive? If so, did you double-check jumpers? Yeah, newer systems and drives it shouldn't matter, but sometimes it does still... Another way is if you have an external drive enclosure... I put old drives in mine, hook up the USB, and test them that way. If there's nothing physically wrong with it, you should be able to recover most of the drive, if not all of it. You may simply need to rebuild the boot sector. I had to do that to recover my sister's system a few weeks ago.... I used some very basic stuff that I have burned on a system recovery disc. I know some stuff is "pirate" stuff, but I have 2 discs I swear by that have helped me a LOT fixing my own system- Hirens and HawkPE. Both have good test and recovery programs.
Does your drive make noise when it is hooked up? If it's loud, it's toast....BUT- there ARE programs that can read info from shot HD's so you can recover most of your stuff, so don't throw it out yet! I had to do that myself when my old PC bit the dust...I was amazed it worked! Another neat trick, someone told me to put your drive in the freezer overnite. Don't remeber WHY, but....oddly enough it worked, and I was able to get most of my files off the drive and onto my storage drive, and the toasted drive was rattling and whining like hell, too,lol!
Let me know how things are going.... You know what you're doing, but I may be able to help you locate programs and such if you are stuck. I don't know what anyone has posted here onsite, but I've seen things in my internet travels... and of course at least that Hirens cd should be able to be acquired legally too....I don't believe it is expensive but I could be wrong there...I just know I can find those things, shall we say, in a "try before you buy" format... you just need to be on a system that can actually burn a cd or dvd for you to use it. And of course, if it performs well for you, you always have the option of purchasing a legal copy because frankly they ARE helpful and handy in an emergency...and as long as you have a computer there WILL be an emergency, eh? Especially if you have a laptop....ONE of the first things to go on a laptop is the hard drive.
drop me a line when you can.
EDIT: Double-ouch...re-read your original post...hardware dying too....ODD.
Unless the system was already dying, it SOUNDS like you may have had something wrong with your power supply. My sister's system, the one I repaired a few weeks ago, had an issue with hers. Her power supply had an external fan that died, and she overheated her system, and somehow her boot sector got screwed up in the process. That's probably one of the first things I'd check, the second thing being to slave the HD to another system and run diagnostic checks as well as antivirus on it. IF you are MAJORLY lucky, you may be able to get away with simply replacing your power supply, running chckdsk, and repairing or writing a new boot sector.
Hard to believe losing all those things at once without some sort of overheating involved. First thing I'd check is the power supply....but come to think of it, see if the processor fan works as well. Yes, it's "possible", but....GENER%ALLY, you don't lose USB,Network,Video,etc. all at once unless you had a power surge or a lightning storm.... this sounds to ME, not having SEEN anything, like it was caused by a power issue.
You didn't happen to smell any burning or heat, or feel any extra heat, did you?
