Hi TroubledUser !
If I'm right the DM051 is the Dimension E510 or 5150.
http://support.dell.com/support/edoc...n/sm/index.htm
(no PS/2 ports and no temp/voltage monitoring utility in the BIOS... great)
Turn the computer off, unplug the power cord, open the case and clean any dust you see with a can of compressed air, focus on the power supply, CPU and video card fans and heatsinks. Replug the power cord, restart the computer and check that all the fans are spinning.
Check that all the cables and pci cards are hooked properly.
Unplug all the USB devices and leave only the keyboard and mouse attached. Retry to boot normally and see how it goes.
See if you have some friend with a good quality 350W+ power supply to test your computer with.