Outlook 2000 and XP Professional

Have an issue with Outlook 2000, All windows and office updates has been done, No Virus software is on the machines at this time. Ok, When a user is on a windows 95 machine and sends a message in the same office, same server the Time sent stamp is correct on the sent item . But the same user can log onto a HP Compaq Evo 310V, windows XP Pro logging onto the Exchange server and sends a message the time sent stamp, is 1 hour earlier than actually sent, checked regional settings, Time, put Atomic clock on it, all updates, Bios included. Contacted HP/Compaq with no luck. The 95 machines is ok, just all the Hp Evo’s.. Any ideas ??