There might be an applicaton your running that is affecting the windows clock.
Gaining time usually has the same causes as losing time. It is generally related to some software installed on the system.
There have been problems in the past with Dell Machines and time. Also some Anti Virus software has been known to cause problems. You can check it out at -
the date and time change randomly by themself
thread779-729783 is a missing thread that had a few ideas that may be worth a try.
I have copied a couple of possibilies from the missing post.
"We had a machine running Win2K that did this as well. It turned out to be the timezone was set incorrectly for the computer's location - go to the timezone tab and check it is set correctly".
That was from "jrbarnett" in that missing post
copy the below into a notepad session, naming the file fix_time.cmd
***** begin copy/paste below this line *********
net stop w32time
w32tm /unregister
w32tm /unregister
w32tm /register
net start w32time
********* end copy/paste above this line ******
That was from "Bcastner" in the same missing post.
Double click on the file to run it.