I think I have a PSU problem, but I need a second opinion

Put together a new system for my Uncle. I am very familiar with building systems, but for this system there is a first for me. I've never build a system with a 7950GT or an Intel Duo COre2 E6600.

Spec:
Gigabyte 965P-S3 Mobo
Intel Duo Core 2 E6600
Corsair XMS2 2GB DDR2 in Dual Channel Mode
Tech Spec:
Capacity 2GB (2 x 1GB)
Speed DDR2 800 (PC2 6400)
Cas Latency 5
Timing 5-5-5-12
Voltage 1.9V
Seagate Series Barracuda 7200.10 Model ST3320620AS
XFX 7950GT 512MB HDCP Extreme Edition Video Card
Rosewill PSU
Tech Spec:
ATX 2.01
Maximum Power 550W
Fans 120mm Blue LED Silent Fan
PFC No
Main Connector 20+4-Pin
Dual +12V Yes
SLI Support No
Modular Cabling Support No
Hold-up Time 16ms min.
Efficiency > 70%
Over Voltage Protection YES
Overload Protection YES
Input Voltage 115/230 V
Input Frequency Range 50/60 Hz
Input Current 12A @ 115AC, 6A @ 230AC
Output +3.3V@30A, +5V@50A, +12V1@18A, +12V2@18A, -12V@1A, +5VSB@2.5A

Installation of XP went without any issues. Once installed I loaded the latest board drivers, bios update, and all XP updates. It was when I tried to load one of the optional mobo programs to monitor fan speed I received an error stating that one of the installed files was corrupt. I tired again and received the same message.
I then tried to install Norton Systemworks. Install was going fine, but then I received another error stating a file was corrupt when loading. I became suspicious because I use this CD all the time and never an issue. I then downloaded some updates to the hard drive and during install it said that the file was corrupted.
I decided to switch out the DVDROM drive with a tried and true CDROM player and using the same Norton's CD I no longer got the file corrupt error, but I was still getting corrupted file errors on files I was downloading. This was perplexing to me as up to now the system seemed very stable. I also thought it might be the memory as I did receive one instruction at ox79c910f29 error.
Then it happened, while browsing the net, the computer rebooted itself. This has happened twice since. I'm starting to think it may be the PSU, but would it also cause programs to behave erratic causing error with installation of files, or memory instability?
I'm wondering if the PSU needs to be updated, do I have a faulty Video Card, is XP corrupted, and is the memory bad?

Any suggestion?

I think that while this may be a psu problem, it would be pretty far down the list. I really think this would be either ram, hdd or a bad XP install.

or swap taht HD out and put it into your computer and see how it goes, possibly faster than "repairing" or reinstalling xp.

I 2nd running memtest.
Its the first thing I would do in your situation. Also I would double check the timings/freq/voltage of the RAM in BIOS.

As for the PSU, if you can borrow a PSU tester, that would be helpful. Or swap it out for another one you have.

Hope it gets working soon!

Thanks to the team here I have isolated the memory problem. One the memory chips failed miserably during memtest. I tested it twice to make sure it would fail both times.
Since I installed all programs including XP under using the bad simm I will do an entire reinstall of XP.
I will probably swap out the power supply as well. I'm looking at the CORSAIR CMPSU-520HX, but wanted to keep it under $100 incl shipping.

Thanks,

Too many PSU choices, but I am familiar with the models you listed. I will do some research, but I am very interest in meeting the power requiremnets and something very quiet. I had an Enermax that was solid, but too loud.

There is an old saying when there are too many choices. You pick pick until you pick #$%@!

Thanks