Disable Hibernation
Most people don't use the Hibernation feature of Windows XP. If you are also not going to use it, make sure it is disabled. Windows reserves an amount of disk space for Hibernation, which equals the amount of the installed memory.
To disable Hibernation, simply access the Power Options inside your Control Panel and click on the Hibernate Tab.
Uncheck the "Enable hibernation" box and click "Apply".
This tweak can free up large portions of disk space for people with larger amounts of installed RAM.