"unexpected interrupt" during memtest

Hi everyone,
I am attempting to run diagnostic tests to figure out the source of multiple BSODs (in addition to a variety of other errors including missing and corrupt file messages) that have caused my computer to continually crash and reboot. I started running memtest (from a bootable ISO file on CD), and about 10 minutes into it, it stopped working and gave me the message "Unexpected Interrupt - Halting." Can anyone advise me as to what this might indicate and what I might try next?

BTW, please forgive my ignorance - I'm not terribly tech-savvy. I appreciate any help anyone can give.

Not sure what info you might need from me, but my computer has an Athlon 64 SATA hard drive; only 512 MB of RAM installed, runs Windows XP Home with SP 2 (actually, I had attempted to download SP 3 but I think it crashed in the middle of trying to install this). Please let me know if any other info or specs are needed to help figure out the problem(s).

Thanks a million!!