I have a three year old Toshiba Satellite M45-S2653, dual boot Ubuntu Jaunty / Win XP for the last year or so, and for the last week it has become almost unusable on both OSes. On Windows it boots but freezes after a few minutes with no apparent reason and on Ubuntu it usually failed to boot or rebooted by itself. I suspected hardware failure of some sort but at the PC service shop I took it they didn't find anything, though admittedly they didn't run any thorough tests. After days of trying unsuccessfully several things, I came across an ACPI troubleshooting page and after disabling the ACPI, the problem on Ubuntu seemed it was gone. Unfortunately it didn't, it only made the random reboots less frequent but it didn't eliminate them. Disabling more stuff (acpi=off pnpbios=off noapic nolapic noapm) gives me the impression it generally helps but no combination has remained stable for more than an hour or so. I downloaded the latest Knoppix and booted from cd (with acpi=off again) and although it appears more stable than the Ubuntu hdd partition, even that rebooted after some time.
Any ideas what might be wrong and what to do about it ? Or perhaps easier, any ideas what *cannot* be wrong ? It's certainly not an OS/software issue since it occurs on all 3 different OSes I tried, so it must be hardware and/or BIOS. I upgraded the latter from Toshiba to no avail. I still suspect it's hardware because if it was only BIOS, why did it happen now and not from the beginning or when I made it dual boot and installed linux ? I didn't have to disable ACPI before, although the suspend/hibernate never really worked on Ubuntu.
While the system is still working, be sure you concentrate on backing up, copying off all your data.
The chances of someone here being familar with all your various boot OSs is unlikely. The only way to rule out non-hardware problems on a system like this is to remove all the partitions, format a single clean partition and see if it runs well.
BIOS won't make something you haven't changed start having problems.
Will the computer sit at the BIOS screen for hours without error?