Back story- Have an old Dell desktop that had a Win 7 32 bit system with a parallel port to use Mach3 to run my crappy little 6040 cnc (I know, I know, but it worked for us). The computer hard drive died and needed to be replaced. Took it to a shop and they installed a new hard drive with Win 7 Professional Service Pack 1 32 bit system. When I tried to open Mach3, the computer would reboot. Took it back to the shop. After investigating, the tech person sent me this message- "After researching for what seems like days. There's an update in windows 7   "A Windows 7 security update has affected those who use Mach3 and Mach4 with a parallel port connection. Basically, when the parallel port is used to control your machine it "takes over" the operating system and the new update does not like it, so it crashes the whole system.". But I was running Win 7 before with no issues. Someone in another forum suggested "rolling back" the updates, but rather impossible since it's a fresh install. Did I maybe have an older version of Mach3 on the old computer? Does anyone have any suggestions?

There was an issue with Mach3 and Windows update. This appears to have been addressed by Artsoft in their patched version of Mach3 (R3.043) which can be downloaded from here:   https://www.machsupport.com/downloads-updates/mach3-downloads/
Load this version of Mach3 over the top of your existing installation (make a back-up of your existing Mach folder first, just in case you need it).

Hope this helps.

Tweakie.

That's the version I got off of the website, and it's the version that is making the computer reboot when I try to open Mach3. After more investigating, I did notice that the Win7 that was installed does have a total of 17 updates it wants to install (some 'critical', some 'optional'). Kind of scared to update it, but I think I can restore it to before updates if I need to (sorry, I'm NOT tech-savvy). Maybe since the updates didn't actually install yet, whatever fix they put in that Mach3 version causes a different reboot issue? I'm really grasping at straws here. I'm wondering if I'll have to get a usb to parallel adapter and try running through the plugin instead. Just hate to waste $ on the adapter if that's not the real issue and/or won't get Mach3 to 'talk' to the cnc.

It was worth a try 

Unfortunately the USB to Parallel Port adapters don’t work with Mach3 so, in the absence of anything else, perhaps your best way forward is to use an External Motion Controller such as (and just for example) the Warp9TD Ethernet Smooth Stepper.

Tweakie.

UC100 works fine with Mach 3.

So I've been doing some experimenting. Found out that it's the Mach3 driver that is somehow causing the computer to reboot when I try to open Mach3. Tried a few different versions of software. One had driver version 4. something, it caused reboot when Mach3 was open. Updated driver to 6. something, still caused computer to reboot when Mach3 was opened. I am at a loss since this is the same computer that was running Mach3 fine and dandy 2 weeks ago with nothing changed other than the hard drive and fresh Win 7 Pro 32 bit system that I haven't downloaded any updates for yet (Can't remember the version that was on old hard drive, other than Win 7 32 bit). Next I'm going to try and install the recommended updates to see if that somehow fixes anything.