In addition to El Gurus hint another one (we're using this thingy for ages on our Windows Server Farm at the office after a server crashes)
While having stopped the spooler service, travel to C:\WINDOWS\system32\spool\PRINTERS and remove all content named *.SHD (Spool header, description of what's coming) and *.SPL (Spool, the print data). The SPL-files can grow quite big, depending on the type of printer (-language) and the type of document, i.e. some 200++-pages PDF printed to a LaserJet 4 Compatible (using PCL 4 (or 5? Not sure...) ) can truly use huge amounts of hard disk space.
After that, start the spooler service and you're ready to go.