It should work for XP. Here's some instructions that I have saved to use to help others..
1. First fire up Registry Editor by typing 'regedit.exe' in Windows 7/Vista Search Bar. If you get a UAC prompt, hit 'Yes'. In Windows XP bring up the Run command using Winkey + R.
2. Now Navigate to this key, to do so simply keep on double clicking the folders till you come across to
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\TimeZoneInformation
3. Right click on the empty space right below TimeZoneKeyName and create a new DWORD(32-bit). On 32-bit versions of Windows 7/Vista/XP, you will only see DWORD
4. Rename the new DWORD as RealTimeIsUniversal (without quotes and its case-sensitive)
5. Double click on the new DWORD and change its value data 0″ (thats a zero) to 1″ (one). Its in hexadecimal
6. Save it all. Reboot to Mac OS X, set the time properly and now boot back to Windows. You should notice the time should be the same as it was set in OS X.