We're using the M100 platform and were wondering if anyone knows of a way to make it run on 900Mhz instead of 2.4Ghz.

I've seen some information about a ground station system for PC that somehow runs at 900Mhz, but it feels like it's an outdated product I'm running across.

Any information would be greatly appreciated.

I don't believe you can given that it uses a Inspire 1 RC, which is hard set to 2.4/5.8 depending on whether you run the rig as a single or dual operator. Based on what you've provided, you ran into the LK900, which was a 900Mhz datalink to use with PC Ground Station. That's a very old accessory that's been discontinued for some time.