Hi,
this is a Mach4 Discussion board whereas your enquiry is about Mach3 and you will get greater assistance if you post on the Mach3 Discussion board.
Bryanna has indentified three updates that have caused issues with people running a parallel port with Windows 7 as OS. There are three alternatives:
1) Find and un-install the three updates and keep your PC off the net to avoid future updates.
2) Buy an external motion controller like a UC300 or Ethernet SmoothStepper, the update issue affects the parallel port only, external controllers are unaffected.
3) Upgrade to Mach4....its a much more modern program and is unaffected by the updates and is additionally still is active development and gets updated itself regularly
unlike Mach3 which ceased development five years ago.
Craig