I don’t know about today, but the second Tuesday of every month is Patch Tuesday (which would have been last Tuesday) – that’s when MS releases new patches and fixes for XP. Maybe your work computers are a week behind?
The skipping sounds like an audio driver buffer problem. Either it isn’t large enough to cope with higher levels of extended CPU usage, or they aren’t robust enough. First try updating your audio drivers, if updates are available. Unfortunately the sound buffer is a hardware issue and can’t be fixed with a simple slider or patch.
Alternately, when playing MP3s, you can try and set your MP3 player’s thread priority higher. Go into your task manager (I assume you already know how to do that if you can see what process is eating up your CPU), right-click on the process name for your MP3 player (winamp.exe for example), choose the “set priority” sub-menu, and set a higher priority.
IE is always a hog. Use Firefox if you want a slimmer, more resource-friendly browsing solution.