The problem is not the G2M, but with your 5-pin MIDI input.
Was your previous computer 64-bit Windows? 64-bit Windows needs different drivers than 32-bit windows. If a device uses standard "class-compliant" USB descriptors, the drivers are built-in to Windows (our i2M musicport does this). It sounds like your device doesn't use this and needs it's own drivers. What device is it? If it needs its own drivers, perhaps there aren't any available for 64-bit Windows. If that's the case, you won't be able to use it.