epiphany moment!!
what version of Windows 7 are you running?
32 bit or 64 bit?
go to >> windows explorer >> left click on "my pc / this pc", select properties and it will tell you the version, service pack and bit version.
Extract from the NFS website on mach3 requirements:
http://www.machsupport.com/software/mach3/Software Requirements
Mach3 Minimum Recommended Requirements:
Requirements if using the parallel port for machine control:
Desktop PC (Laptops are not supported) with at least one
parallel port 32-bit version of Windows 2000, Windows XP, Windows Vista, or Windows 7
(64-bit versions will not work) 1Ghz CPU
512MB RAM
Non-integrated Video Card with 32MB RAM(Large G-code files, especially 3D files will require a video card with 512MB RAM or higher)
Requirements if using an external motion device for machine control:
An appropriate external motion controller (options can be found on the Plugins page)
Desktop or Laptop with Windows 2000, Windows XP, Windows Vista, Windows 7, or Windows 8
1Ghz CPU
512MB RAM
Video Card with 32MB RAM(Large G-code files, especially 3D files will require a video card with 512MB RAM or higher)