Multiple problems+ BSOD!

[modivo]

I have a 2009 Dell Studio XPS 435 MT Desktop, OS Vista Home Premium 64 bit, SP2.
Over the past several months, I have encountered multiple problems beginning with:

1. No Updates would install. (HTKEY (sp?) was missing & I couldn't replace in Windows system 32 files)
2. Couldn't download anything from software updates- new programs
3. Unable to receive email from any account: POP 3 problems.
4. While trying to start, PC continuously stuck trying to install update 3 @ 0%.
5. BSOD

I have spent countless hours, days, nights-months trying every fix I can find on the internet. None of the MS fixit tools would download. I've long succeeded the term limits for Dell support.

Today I have tried to run Safe mode, Repair mode, System restore, even tried the OS from the DVD & nothing works. I was only able to get
ERROR 2000-0146, which indicates there is something wrong with my main HD. I tried to restore the BIOS to default settings which did not help. I am currently running the Dell extended system scan...

I have already gone through the initial list & menu options to boot. Does anybody have some detailed ideas on what else I can do other than a clean install? I see that as an easy out, although it's probably better than losing my sanity at this point!

I have intermediate computer skills & have no problem working with the insides on my pc.

With 2 kids in college, dumping this for a new pc is not an option.

I appreciate any help the experts out there can give!