if you have recently installed any programs they can create ramdisks in xp. There are other utilities similar to this. People often use this as a temporary folder as it creates the disk from your RAM ( memory ) and it gets viped out everytime you switch your pc off/on.
As i cant see how this have been installed in your system check these out.
Goto Start > Run > type "services.msc" without quotes and on services list look for "RamDisk" and if there is a listing and its started as a service simply stop and disable the service.
Eventually you can check it in Windows Registry.
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Ramdisk\Parameters