Try the Disk Cleanup Wizard. I know it sounds lame, but bear with me.

After the Disk Cleanup wizard has scanned your drive, go to the "More Options" tab, and there's a button to remove old System Restore checkpoints. Every time my 250gb laptop drive gets full, I just clear out the old restore points and hey presto, another 30gb magically appears. (This 30gb does not show up in your Windows folder, it's a hidden system folder in the root of your drive under System Volume Information).

Worth noting that if you use Shadow Copies, it will also delete your shadow copies, so don't do this if you want to keep revisions of your files in this manner.

I should also second shufler's comments - 10gb is not a big Windows XP install. I just checked mine and it's 7gb exactly (you should see the SxS folder that Vista insists on balooning out, on my Vista machine it's 15gb on its own).

Also, this question really belongs over on super-user.

Try the Disk Cleanup Wizard. I know it sounds lame, but bear with me.

After the Disk Cleanup wizard has scanned your drive, go to the "More Options" tab, and there's a button to remove old System Restore checkpoints. Every time my 250gb laptop drive gets full, I just clear out the old restore points and hey presto, another 30gb magically appears. (This 30gb does not show up in your Windows folder, it's a hidden system folder in the root of your drive under System Volume Information).

Worth noting that if you use Shadow Copies, it will also delete your shadow copies, so don't do this if you want to keep revisions of your files in this manner.

I should also second shufler's comments - 10gb is not a big Windows XP install. I just checked mine and it's 7gb exactly (you should see the SxS folder that Vista insists on balooning out, on my Vista machine it's 15gb on its own).