>>Have you tried running System Restore on the balky Dell? IIRC you have to press F8 before the Windows logo appears, then follow the prompts. That's for Win7 and I'm sure is slightly different on earlier versions. I had to do that recently on one of my daughters' PCs.
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>I am sure its hardware, as most of the time it does not even reach the point where you can press F8, it just flashes the power for 10 seconds or so. Other times it might even reach the start of windows, but only once in a hundred times, and then dies.

The Dells my clients have bought over the years have generally been pretty good.

One client bought a batch of Dimension 5150s in 2006, all their power supplies have died and been replaced. In those cases, the computer won't start at all.

If you have problems serious enough that the computer won't start to boot Windows:

1. Try booting from a LiveCD such as Knoppix. If that won't work, most likely you do have a hardware problem

2. You may have bad RAM memory in the first GB. If your RAM is in 2 or more banks, remove the first bank completely and replace it with the second. Try booting with the bare minimum of (hopefully good) RAM.

3. You can test RAM with MemTest86+ (bootable CD): http://www.memtest.org/

4. Simplify the hardware: unplug all exterior connections except power, keyboard and monitor. Remove all expansion cards except for video if that's what's being used. Although, if the computer also has integrated video you could plug the monitor into that and remove the add-on card. Disconnect unnecessary internal devices. The ultimate test, if nothing else works, is to disconnect all internal devices except the CD drive (i.e. disconnect the hard drive) and see if you can boot Knoppix.