Thanks Tweakie.
This is a bit of a long shot.... are you logged on to windows with a non administrator access account?
Can you go into the mach3 folder (c:\mach3\), then select view by details, and select sort by type...
Go down to the exe files, and left click on each one, and select run as administrator...
It's a long shot, but worth 5mins try.... windows may be blocking the running of something because your account settings do not have administrator rights or something is up with your antivirus being over zealous...
Sorry, running out of ideas