From my experience printers often cause PC's to operate painfully slow. This leads me to believe there is nothing you can do about it. Except get a faster printer perhaps? As long as the PC resumes back to normal speed after printing I dont think there is anything wrong. This is probably not the answer you wanted.
On my old computer when using my old Epson 460, everything used to slow down. Now with 512 DDR and Pentium4 2.4GHz erything is like lightning. I know nothing about the inside workings of computers, but could CPU speeds and memory have something to do with this problem?