Why does my computer clock keep changing?
 

As per title, really:)

Thanks, Alcazar

If you mean resetting, then you need a new battery for your bios backup. Basically you are switching off the PC - and the CMOS is clearing to factory settings.

your PC might be synchronising with a time source on the internet somewhere.

as above or

Click on your clock to open it

Click Internet time see if your clock is synchronizing with
time.windows.com
time.nist.gov

I noticed my was loosing time for some reason seems spot on now ;)

when installing windows did you accept the default time settings which i belive is -8 hours and now your clock is going back all the time. double click on the time (if youre using xp) and check the zone settings i.e. GMT. windows. like elgordano said windows may be pulling the time off the net and putting the clock back