i am using Dell optiplex 990, since few days it has power supply problem. In start i press the power button it start and as it reach on windows 7 flower iit goes to power off. i have done following things. i. Clean the dust ii.swap the ram. iii. Paste on the processor. Tell me if it is the fault of power supply and how i can solve it?

Regards

Shahzad Majeed