Parallel does NOT support hot-plugging. You may have damaged the port, and now the lines are floating, and triggering a constant interrupt stream in the background, bogging the machine down bigtime. There are some real-mode DOS printer-port diagnostic tools out there, I would make a bootable floppy and try one of them, and see if the port is fried. Otherwise, you can narrow it down to software issue in Windows.
Also, check if STISVC.EXE (I think that's the one - WIA service) is running, and stop it if it's the one hogging the CPU.