My computer clock runs slow!

My computer clock runs slow! A few minutes a week.

STEPS to fix ALREADY TAKEN:
I have changed the MB battery (2 times in the last year). Still running slow.
About 2 years ago I put in a new power supply and a new hard drive.
The MB is an ASUS P4B533 (about 9 years old) with a P4 1.7 GHz chip.
Running Win xp sp2

Any suggestions on what would STILL cause the clock to run slow and WHAT
STEPS I MIGHT TAKE to fix it?

Is there any program that I can put into my start up folder to run, check
and automatically adjust the clock each time i boot up? (I do not think that
the Windows time synchro can be set to run at boot up. It seems that it can
only be set to run once a week)

thx