And the CPU?
Thanks for your reply. Info (as best as I recall) as follows:
PSU is a Casecom ATX 500W, Memory is DDR2 - 2x1GB "Value Select", and 2x2GB "Crucial" - can't be certain of voltage - probably 1.8v. CPU is an AMD Athlon 64 socket 2 - standard clocking and has never been overclocked.
System failure message bit of a puzzle all around - I haven't yet started taking the RAM modules out to check on compatibility, - belief that if it works under Debian, it should work under MSW7. Does this additional info give you any clues?