cdos, please list the model numbers of *every* component in your system, including things like cpu cooler, power supply, motherboard, all RAM, etc, so we can help figure out what is going on.
You can download memtest86+ as a bootable CD image as well as a bootable floppy image, so you should be able to run it no problem. It definitely sounds like something is not working right; if you had hardware problems, your installation of Windows may now be corrupted, so it's best to get your hardware working properly, then reinstall Windows and your other apps.