system time running slow

hmm I have a wierd situation: I have a somewhat brand new p4 with a new motherboard and everything... It's just that every 1 or 2 months the system time seems to be behind the official time by 2-5 minutes. I keep synchronizing it and it keeps falling behind after a while. Is this definetly from the clock battery? or could it be something else?

my partner had a DELL with the same problem. At first they told up to just update it, then we had to download a new CLOCK.EXE program. It used to be nuts, off by 12 hours in a month!