I get a BSOD, despite replacing the hard drive

[plec]

I'm at my wit's end here.
So I've had a computer now, for about two years. I use it to do schoolwork, play tf2, post on a forum, nothing major.

But I swear, it's like whatever I use with the computer only has a short amount of life before failing.
I got the computer from a more savvy friend. He constructed it from a lot of spare parts, but I know he knew what he was doing, as he'd been working at a computer repair shop for multiple years at the time.
Only a few months after receiving the computer, I started having problems, used Google, and learned the problem was one of the RAM sticks had failed. I found the defective one, took it out, and thought nothing of it.

Since the two years have passed, I have had the power supply explode, installed a new fan since the computer ended up overheating, lost the use of a usb port, ended up losing usb devices any time I turned off the computer and left them attached, took out another ram stick, and now I'm getting hard disk problems.
Each time I started up my computer it's a crap shoot. When it's working, there's about a 1/4th of a chance it won't boot up, and I have to spend at least an hour getting it working again, by unplugging everything but the keyboard, or enabling bios settings, or using chkdsk.
Speaking of chkdsk, the damn thing is detecting tons of errors constantly. No matter how many times it fixes it, it comes up with new ones the next time.

Right now I've got very little money. Fortunately I won a 70 dollar external hard drive in a silent auction. The plan was to attach it to my computer, make it bootable, and wipe my hard drive clean. I only paid 40 bucks for it as opposed to 70, but it was still pretty aggravating to see it fail on the first try. I got an I/O device communication error, and it wasn't working with any other computers, either.

Just a day ago I discovered a new error. I'm now blue-screening, due to either a bad boot header pool or a irql neither-greater-or-less error. Now it's impossible to start up the computer.

By using another site, I was able to determine the culprit behind my failing parts was my Ultra Lifetime series PSU. I had gotten the same kind after the first exploded, since at the time I was unfamiliar with PSUs and wanted something I knew was appropriate for the computer. However, I'm still unable to recover my computer. I even tried using another hard drive, and yet I still get the same blue screen! I have two sticks of RAM, and have tried to see if either is corrupt. I took one out, and it behaved normally. I put the first one back in and took the second out, and this time the computer just freezes before giving me a blue screen.
What on earth is malfunctioning? Everything?

 

[MvdB]

Hello Plec, welcome to SF!

Looks like you have not been lucky with this system. No offence but it also looks like your friend that built it, was not that savvy... or should have told what the risks are in the way he apparently did the build. We know about Murphy's here but this sounds as a bit too much.

It is really hard to give you good advice on the info you gave. Your story is clear enough but we need detailed technical spec's of ALL components to be able to suggest anything....

Some advice offhand... if you yourself are not into computer electronics/parts... then don't add anything to it until you are sure of what you are doing....You wouldn't want a faulty PSU to burn your new HDD.