Suspicious PSU problem

[jamessyy]

Hi. I bought myself a video card, Gigabyte GTX 550 Ti about a month ago but i was getting lock ups in games such as COD MW2. I fixed this problem by disabling the Intel common user interface from startup in msconfig but now i face a new problem. My computer power-offs and restarts when im playing games now and get random 0 FPS lags spikes which last around 1-5 sec from time to time before the computer power offs and restarts. I checked my temps they seemed fine.

CPU idle - 32 degrees Celsius, Load - 55-65 degrees Celsius
GPU idle - 32 degrees Celsius, Load - 54-68 degrees Celsius
I recently cleaned out my CPU heat sink also and reapplied with Arctic cooling MX-2 thermal paste

I managed to stop the power offs by under clocking my GPU to around 600 - 800 MHz from the stock 900 MHz and also the shader clock to 1300 MHz from stock 1800 MHz. However i am not getting the most of my video card so i want this problem fixed.
I am therefore suspecting my PSU as it is a generic 500w "Penguin" brand. This is a picture of it (http://imageshack.us/photo/my-images/4/20121208182528.jpg/).

My specs are:

Intel E8400 core 2 duo @ 3.0 GHz
Asus P5G41T-M LE motherboard
Gigabyte Nvidia GTX 550 Ti
1 TB HD
2x2gb (4Gb) Ram

I also ran furmark but the computer did not shutdown.

Please give me some advice on this problem and if you find anything else wrong dont hesitate to post. THANK YOU!!!!
P.S If it is a problem with the PSU i plan to get the Silverstone strider essential 500w PSU.

 

[jamessyy]

Just gonna post that i bought the new branded PSU by silverstone and now everything works flawlessly.