If you've done defrag fairly recently it's not likely to help much, although it's something that needs to be done on a fairly regular basis so it doesn't hurt to do it again (except the pain of waiting for it to finish).

At the same spot where you do defrag (Right click the drive, Properties), but on the General Tab there should be a Disk Cleanup, where you can also clear Temporary Internet Files. I wouldn't expect the sound sytem buffer to use this space, but once again eliminating the "probably nots" leaves fewer "maybes."

Clearing Temp files, Downloaded files, and History are usually painless. If you delete cookies there, you'll find that you have to log back in the next time you come here - and other places where you have persistent logins. An alternative for cookies is to use Ad-Aware (free download "anti-spyware") that deletes the annoying (and sometimes hazardous ones) but usually leaves "permanent ones" that you've given permission for.

At the Drive Properties, General tab, there's a check box for "Compress files on this drive to save space." If the box is checked, your whole drive may (or may not, depending on Format) be compressed, which can slow down some file operations. I don't see it having an effect on buffer/temp space, but it might be something to consider if/when Jon and Mick run completley out of ideas. If it's NOT CHECKED don't check it, at least for now. If it is checked, I'd suggest leaving it alone until someone can look up how messy "uncompressing" a whole drive may get; but it might be mentioned as information for further thinking in a later post.

I do practically zero sound work on my computer, so I can't really comment beyond the basic system workings. The problem here seems to be tied into how the sound system works, and I can't go far there (and may have exceeded my safe depth already).

John