Doug,
My previous desktop ran Windows XP (now upgraded to Windows 7). I turn it on in the AM and
I cannot recall it spontaneously shutting down. I log, upload/download from LoTW & eQSL,
download from a few of the Internet membership lists, run OmniRig to talk to my radio,
recently got in to digital modes with HamScope and FLDigi.
I would suggest regular hardware troubleshooting tips. Start with RAM. Windows 7 & 8 have
one as part of the diagnostic startup menu. If not, try
Memtest86+73s, Don