my computer clock is going slow?

PC clocks are normally pretty accurate, crystal controlled but can drift. It is poissible to set the PC clock regularly to an atomic clock via the INternet

See

http://windows.microsoft.com/en-US/windows-vista/Set-the-clock#

and

http://tf.nist.gov/service/pdf/win2000xp.pdf

Ticktock man
January 2011