well, you're right, that is bizarre.

i usually enjoy troubleshooting [the problems of others better than my own ].

spontaneous reboots indicate serious problems. usually hardware-related (something on motherboard or psu).

fact that system restore did nothing seems to confirm.

the kicker is normal ops with bootable cd. if problem is hardware-related, how come it doesn't happen then?

seems like the cdrom *does* have some effect. maybe this could indicate a problem with the controller. are the hdd & cdrom on same controller?

any bios updates available?

if you could get your hands on a known-good psu and try that, it could rule out one factor (bad psu).

you say "little used" so i doubt psu is failing. but 2-3 years is not unheard of for a psu to "start" failing.

also could try reseating all connections .. to mobo and drives.

do you have more than just one hdd and one cdrom? in other words, how's the power demands on psu.

i've had these types of problems and the basic approach is to modify variables, and collect data, more and more. hopefully a lightbulb will go on.

this is one of the weirder problems i've heard of.

i'd also try playing with cd drive when system was working normally, to see if that affects anything .. like copying data to hdd from cd.

how is electric in your house? old house? old electric? grounded?

do you have uninterruptable power supply (contains a battery back-up) connected to system? they tend to 'clean' the power to systemand even-out any fluctuations.

more data points = better. something will turn up.

i can see why you're "frazzled".