Eratic Re-start with Random Keys

[mmcdill]

I recently loaded win98SE onto clean harddrive. Weeks later, after I loaded a few other programs, the computer would restart without warning or message (like second time you hit ctrl-alt-del) when delete key was hit, or I was typing quickly, and once when I hit "print screen".

I decided to start over -- reformat HDD, reload windows, and it did it again with no new software added. I changed keyboards -- still does it!

Has anyone heard of such a thing (I searched this forum pretty thoroughly). Any ideas?

Thanks,
Mark