128MB of RAM is a bit low for XP Pro. If your drive is fragmented or has errors, I can see where skips might be a problem.
First of all, I'd open up a command prompt window and run the following:
chkdsk c: /r
The machine will tell you that the drive cannot be locked for error checking, would you like to do this on your next reboot? Tell it yes, reboot, and then read a book while the system checks for errors. When everything boots back up, run a defrag of your hard disks to make sure you don't have some badly fragmented files. Once your disks are all defragmented, try playing your audio files again, and let us know what happens
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