Is My Power Supply Unit or Graphics Card Defective

[robetlndis]

I upgraded my video card from 256MB GeForce 7600GT to a PNY 512MB GeForce 8600GT and used latest drivers.
see: http://www.newegg.com/Product/Product.as…

To use the new GPU, I also upgraded my power supply unit to a Antec EarthWatts EA500 500W
see: http://www.newegg.com/Product/Product.as…

Once I installed both new parts I noticed something was wrong. While I'm using my PC (anything from browsing the web, playing a game, watching TV, or music) the computer will randomly freeze and then unfreeze after about 1 minute. When playing music, the speakers will repeat the last note of the song over and over until it unfreezes, when streaming online video it will fast forward to where it would be if it hadn't locked up.

Anyone have any idea which part is defective? I know its one or the other because my PC was stable prior to the upgrade.

PC: HP d4790y with Vista, 2.4ghz core 2 duo, 4gb DDR2 (used to have 350W PSU and 7600GT GPU)

[Mr. Knowitall]

This is a legal forum, not a technical forum. If you were sold defective products and they fall within the vendor's return policies, try to return them.