About a month ago, I installed a new graphics card (NVIDIA GeFORCE 6200 OC) in my Dell Dimension 2350.  I found out that the 250W power supply was not enough power to run the new graphics card, so I ordered a new 480W power supply.  After installing the new power supply, neither my CD or my DVD drives are working.  They have a yellow ! mark in the device manager.  In device status it says, "Windows cannot load the device driver for this hardware. The driver may be corrupted or missing. (Code 39)"  I tried deleting the registry entries for the Upperfilter and the Lowerfilter.  Still not working.  I put the old power supply back in.  Still not working.

HELP!