New computer keeps shutting off or restarting

[Head On]

First off, I would like to say thank you to everyone on this forum for helping me buy and build a great computer. I'm using it right now and and I'm overall very pleased. But every one and a while it just restarts or shuts down. I have no idea why it's doing it. It is not an overheating or power problem because I've been able to play Company of Heroes and FEAR Combat on it without lag and it works fine. But, I have noticed that it seems to be shutting off/restarting often when I plug in or pull out my headphones into the front panel of my case. Just a few minutes ago I found out that I could get my to computer to restart by plugging in headphones when the computer had just restarted recently (when you can see the desktop but it's still loading startup applications). I have no idea what is wrong or how to fix it. This isn't a huge deal but it's just so freaking inconvenient to have the computer randomly shut off like that. Here's my system specs just incase any of you need to know:

Motherboard: Asus P5N-E SLI
CPU: Intel Core 2 Duo E6400
Memory: (2x 512MB) Kingston PC2 4200 RAM
Hard Drive: Western Digital 250GB SATA-HD
CD/DVD ROM Drive: Not sure. I got it off my old Compaq. It reads DVDs and reads and writes CDs and DVD+R.
PSU: Got it with my Xion case from microcenter. 450 Watts.
GPU: Nvidia eGeforce 7600GT

Thanks for the help in advance.

 

[sanka]

Its probably your PSU. Power supplies that come with the case are usually bad.

Just because you can play FEAR without lag doesn't mean its not a PSU or overheating problem.

Also, make sure your heatsink is in tight and check your temps (just check its worth it!)

 

[PaperPlunger]

yeah, 450w seems low for that setup anyway

 

[AMF]

I had a similar problem that took me weeks to figure out. It boiled down to my motherboard not wanting to run my memory in Dual channel. I didn't understand it because it's matched, but I haven't had a single problem since I moved the 1 stick over a slot out of dual channel. This may not be your problem, but I thought i'd post it anyhow just to be safe. Good luck to ya.

 

[xtremezx2]

try ^^ first simply because its very easy to move your ram and see if it helps.

otherwise i'd say the power supply is the problem. its not that 450w is not enough of a power supply, but its a cheap psu that came with a case and the 12v rails likely can't handle what the video card is wanting.

 

[Head On]

Okay, I'm looking for psu units on newegg and I'm gonna go to micro center or best buy this weekend. I heared I should get dual 12V rails, but what else should the psu include? What wattage is good for this computer? Anyways, as for my ram there are four slots arranged like so: || || (Ones in bold are occupied)
The 1st one and the 3rd one are yellow and the 2nd and 4th one are black. I have 1 stick of ram in each black slot. On the bios my computer recognizes all the memory I put it. I am wondering if it is my cpu because it just restarted about 5 minutes ago and when it came back on (before it loaded windows) it said something along the lines of "Warning! You cpu setting have changed. Press F1 to continue, DEL to enter setup". I don't remember even touching my cpu setting in bios but I'll post the configuration here just in case something somehow changed(its a core 2 duo e6400):
CPU Type Intel Core 2 CPU
CPU Speed 2.13Ghz
Cache RAM 2048K

CPU Multiplier 8
CPU Internal Thermal Control Disabled
Limit CPuid MaxVal Disabled
Enhanced C1 (C1E) Disabled
Execute Disable Bit Enabled
Virtualization Technology Enabled
Enhanced IntelSpeed(tm) Tech. Disabled

I'm not sure if the cpu has anything to do with this though.

 

[Raffaz]

That error your BIOS is giving you is normally to do with a dead CMOS battery. I know its a new build but its common to get a dead battery with a new mobo, so ya might wanna replace that. That shouldnt be causing the restarts tho