You would need to setup a RAMDrive and then follow http://support.microsoft.com/kb/308666 to move the printer spool file to that ram drive in place of a physical harddrive.
In XP, Open Control Panel -> "Printers and Faxes"
From the File Menu, click "Server Properties".
Then on the "Advanced" Tab you can change the Spool Folder to move the spool to another faster drive, raid-0 array, (or in this case, ram drive)
Now that I'm running a 64-bit os with 24 GB of memory, I moved my swap and printer spool directories to a ram drive using qsoft ramdisk on windows 7. So far so good with no apparent problems and no more waiting for windows to run through large jobs in the printer spool. http://members.fortunecity.com/ramdisk/Download/download_and_003.htm
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