PC Problem...HELP!

Ok, so my friend and i built his pc a year ago, it had it's we'll say "unique personality." It just got worse in the past month or so. His PSU died so right now he's power in the following:
Gigabyte ATX Mobo
ATI X1900XT w/256MB
2gb of RAM
Core 2 Duo @ 2.13ghz
250GB Western Digital Hard Drive
Happauge TV Tuner
Disc Dirve(there is no plug going to this so it is not on)

With a, i believe, 350 watt PSU. It didn't have enough cords to hook into his disc drive and now his computer suffers more of the following:
Game Crashes
Blue Screens while in game
Lag

Now, everyone's comp eventually finds that game that their comp doesn't like, we'll his computer hates all games now.
So i'm wondering, what's the best course of action for him:
New RAM?
New psu?
New Graphics Card

Ok, so my friend and i built his pc a year ago, it had it's we'll say "unique personality." It just got worse in the past month or so. His PSU died so right now he's power in the following:
Gigabyte ATX Mobo
ATI X1900XT w/256MB
2gb of RAM
Core 2 Duo @ 2.13ghz
250GB Western Digital Hard Drive
Happauge TV Tuner
Disc Dirve(there is no plug going to this so it is not on)

With a, i believe, 350 watt PSU. It didn't have enough cords to hook into his disc drive and now his computer suffers more of the following:
Game Crashes
Blue Screens while in game
Lag

Now, everyone's comp eventually finds that game that their comp doesn't like, we'll his computer hates all games now.
So i'm wondering, what's the best course of action for him:
New RAM?
New psu?
New Graphics Card

A 350W PSU shouldn't have any trouble powering that - so that's unlikely to be the problem.

Sounds like a software problem, and by that, I mean, it's Microsoft.

Try updating your video drivers, chipset and look for a patch for the game.

Also, if you are running Vista, try running the game in XP compatibility mode, seems to help for some games.

Like TheBeast said, it's probably not an issue with the PSU.

If your power supply has died how are you able to even turn on the PC to get game crashes, blue screens, etc? If that has died then you should definitely get a new one (preferrably one no less than 500W and with enough connectors to power everything including your disc drive).

I agree with JDM006, it seems the computer is not getting enough juice.
@Bullet_Jr, none of the suggestions you mentioned have anything to do with Microsoft, all drivers you mention are from other companies.

What OS is he running right meow?

He's running Windows vista w/SP1
Every blue screen he gets mentions a hardware failure. Personally i think it's his RAM or Graphics Card and i also personally feel that while 350 watts may be plenty to power it, it's always godo to have a little more than you need.

RAM Issue started after i tsted some bad RAM in his system (i was testing the RAM to make sure it was truly bad and not some other part of another computer)
Graphics Card is one i sold too him i'd say a little more than a year ago, and it's been put through it's paces, i had it overclocked and unlocked it when i sold it to him.

So it could just be those bad parts, i personally don't think it's a software issue, as i've built 3 computers, one with xp, two with vista, his comp is the only one with problems that's hardware related. The other person whom i built a comp for got viruses on it....

But anyways, yeah ignore my tangents.

Sounds like it could be one of two things. Either that the new power supply is under delivering (meaning it may say 350W but it could be putting out closer to 250), or you're overheating. 

I don't think it's the RAM with 2 gigs in Vista he'd be seeing a lot of the blue screen just doing everyday things (if you want to test the RAM look for a program called memtest www.memtest.org it's worked for me in the past).  

Well i just talked to him, and he said he does have random crashing when he's browsing the internet. So i'm going to have him run memtest, and then buy some new ram.