[Dulled by Excess]

If you're able to play mp3's from your primary drive, adding more RAM isn't likely to be the solution. Adding more RAM is still never a bad idea, though. How do you currently have the drive set up (Primary Slave, Secondary Master/Slave)? Do you know the drive's specs (speed, cache)? How old is this drive? Was the problem fixed earlier by closing TSR's and background apps? What did the XP Disk Checker find (it's most likely running chkdsk)? Any bad sectors?

"Back in the day", mp3 playback was considered extremely resource-intensive, but if your machine is anywhere near recent, you shouldn't have any problems playing mp3's. Likewise, if your machine runs windows XP and has at least 128MB RAM (although I wouldn't recommend anything less than 256MB), you shouldn't have any problems playing mp3's.