Solution To Slow Cutting Through Printer Ports After Installing Certain Model HP Deskjet Printers:

Models we know about:

-HP Desk Jet 640c & later
-HP Desk Jet 840c & later
-HP Desk Jet 930c & later

HP have introduced a feature called HPIO, which continuously monitors the parallel port state. This causes interupt to the data flow through the ports. 

ZIP drives that hang or refuse to save data, parallel port scanners that go offline or hang during scanning, and plotters (all types) that are connected to printer (aka parallel) ports.

In Windows, go to Start, Programs, HP xxxx, HP xxxx tool box. The "xxxx" refers to the particular model HP printer

Right hand mouse click on the printer icon at the top left of the tool bar, ie immediately to the left of the letters "HP" and then click on "about"

Holding down the control key, double click (using left mouse button) on the printer icon at the centre of the dialog box. Push enter twice until a dialog box appears with the word "configuration" at the top. Sometimes it is not necessary to push enter key if only one Deskjet series printer is installed.

Click on the menu item that says "Remove HP IO", and remove it

Close down all related dialog boxes and restart computer.