Audio Problems

My audio will play however the audio track sounds like it skips. It does this on CDs, music from the hard drive, and streaming audio on the internet. I have tried new drivers and doneall the diagnostics to no avail. I did a system restore and the problem went away. However, once I re-installed the Windows Updates ( 9 of them ) the problem returned. Any ideas on how to isolate further besides installing 1 update at a time and then checking for the problem to return? I have a Dell D600 with a WinXP Pro operating system.

Lindsay