|1) often this is caused by automatic windows updates: it installs an update that requires a reboot and will do it immediately - simply ignoring that some user is logged on currently!|
with windows xp professional you can use gpedit.msc - there's a policy that allows you to disable this kind of behaviour.
you need to enable the policy “No auto-restart for scheduled Automatic Update installation".
however, windows xp home does not include gpedit.msc.
there's another solution: re-configure the automatic updates to "automatically download but let me chose when to install".
the title is a bit misleading. even if you do not manually chose to install the updates they will be installed when shutting down windows.
for full details see: http://4sysops.com/archives/turn-of...
2) in case the automatic reboot is caused by some fatal error:
disable the automatic restart (as already suggested by kenross). you will also find some according entries in the system event log.
3) sporadic reboots may also be caused by overheating due to poor system cooling.
4) last but not least you should ensure that you have all required microsoft patches. you need to manually go to the following url, once: http://update.microsoft.com/microso...
this is to install the component "microsoft update" on top of "windows update".
for complete analysis it would be important to know:
- did those restarts start occuring just recently or has it always been like this at your computer?
- how often does it occur? once a week? twice a day?