either both use UTC or both local time.
In your case, one is UTC, the other is local time. Suppose linux shows 13:00, and windows shows 5:00, then linux must be using UTC and windows using local time. Because linux "think" it's UTC 5:00.
It seems Windows XP can only use local time. Correct me if I'm wrong.
In linux, check /etc/sysconfig/clock
I don't know Mac