don'tkno isn't looking to add another drive at the moment. The problem is choosing what files and even folders to remove. Those will have to hand picked to avoid deleting anything important or simply unreplaceable.
The main problem is gaining acess to the drive. This has to done manually by booting with a prepared XP boot floppy, installation disk to the recovery console, or even much easier a live for cd Linux distro like Knoppix Live. Something like those mentioned would be needed if not slaving the drive in another case to manually delete files through a command prompt.