Vista requires a two stage installation!
Step 1: Delete the Mach3 installation completely.
Step 2: Make sure the directory C:\Mach3 is removed.
Step 3: Install Mach3 , it will prompt you to install the driver, make sure you check the install driver option during the installation.
Step 4: The installation will prompt you to reboot, make sure you reboot.
Step 5: download the file "memoryoverride" it is attached to this post.
Step 6: Run the "memoryoverride" program, just double click it.
It modifies the registry to allow MAch3 driver to run.
Step 7: Go to the C:\Mach3 folder, (or wherever you installed Mach3) and right click drivertest.exe , select "Run as Adminstrator.". It should tell you to reboot. Do so, or you will crash. No question about it..
Step 8: Run the drivertest.exe again, and it should run.
You may get errors reported when running DriverTest, in fact it may not run at all first time, then
Vista will ask you if you wish to run it in compatability mode. DO so, and it will run..