prezzhax,

Cleaning and applying the arctic silver is a good step and should always be done when the assembly is removed and reseated.

The Dell bios will only boot from Dell OEM (original equipment manufacturer) operating system CDs. To boot from a non-Dell CD, you would have to boot from a floppy disk or a USB key, then access the non-Dell CD.

When you power the PC on, what color are the Diagnostic Lights?
http://support.dell.com/support/edocs/systems/xps400/sm/adtshoot.htm#wp1054184

The Power Button Light?
http://support.dell.com/support/edocs/systems/xps400/sm/adtshoot.htm#wp1054148

DELL-Chris M
Dell Community Desktop Liaison