Why does Ubuntu 9.04 reset my Windows clock?
Is it this problem?
You need to look at/etc/default/rcS
and change UTC=yes to UTC=no.
This makes Ubuntu read and write to the hardware clock in the same way as Windows, using local time instead of UTC.
If you prefer to make the change to the windows installation:
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\TimeZoneInformation]
Add a new dword named "RealTimeIsUniversal" and set it to 1