Hello all I'm new to the forum so be gentle, I just built a new computer last week the first couple days the computer ran great with no problems except I found it weird how when I first turned it on and every time I turn it on it starts then shuts off for a couple of seconds then turns on again for a second time and continues to boot up. Isn't that kind of weird? Well anyways so I didn't think anything of it because it ran fine, I first noticed the problem the first night I left the computer on all night to download some files and the next morning I realized it restarted sometime that night, and it did it again that day while I was at work. Still didn't think much of it until I played the game FEAR for about 7 - 10 mins into the game then all a sudden the whole screen was covered with artifacts so I quit the game to the desktop and they where still there. It does this every time I play the game and I have temp gauges to watch the cpu and video card the video card hovers around 70 c and the cpu in the low 50's. So I don't understand why I'm getting these artifacts. Also several times the computer froze at the windows boot up screen at start up. Also it restarted on me once while I was surfing the internet. The reason I ask if the power supply is powerful enough is because I didn't order one so I borrowed my bros out of his computer and its rate at 384 watts and 430 watts max I think maybe its 430 sustainable watts I'm not sure and my system is:

Intel Duo Core 6420 at 2.18 Ghz
2 Gigs of DDr2 ram
400 gig harddrive at 7200 rpm
ATI Radeon X1950 Pro 256mb ddr3
Integrated 7.1 dolby digital sound
Abit IP35-E Motherboard
Windows XP home edition
Pioneer Dvd Burner

I think thats most of the important stuff it says the motherboard is rated at 400 watts and the video card is rated at 450 watts am I giving them enough juice, if not would it cause this stuff to happen and how much juice should I get? I also don't understand because I played doom 3 for like 4 hours the night before all this **** started and to happen and it worked fine, but that was before I let it run all night.
Need help ASAP thanks you all in advance!

Bump
Please help need opinions with same experiences

Could you check the Brand of that PSU ?

Please note-- depending on it's age-- all power-supplies lose a little bit every year due to capacitor aging-- plugging what hardware you have listed into my "Power-supply calculator" came up with 308 Watts-- so if you are pushing it hard --and it is older --or not the best brand to begin with-- the PSU would be very "border line".

Gaming pushes everything to the hilt-- so a questionable PSU is not good. You could take it to a local shop and have it tested-- if you take it out does not cost much.

Its and antec.

Old/new-- ? How many years roughly...