Hi Lucas,
Checkout the installation of Mach3 on this computer.
Under some circumstances (AFAIK depending on the version of the installer), the entries in the registry are not complete.
Check for those or insert them:
Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Mach4.Document]
@="Mach4.Document"
[HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Mach4.Document\CLSID]
@="{CA7992B2-2653-4342-8061-D7D385C07809}"
it should work then.
best regards,
Steffen