Try this software. You can download the demo and use it for a few days. It costs $40 full version. Easy to use and if you donate to RadioReference.com it'll automaticly set up the different systems.
I know your looking preferably for free, but I purchased the Uniden software for the 246t. (about $30) That with assistance I receved from members on this site, helped me with all I needed. Except for 1 frequency I programmed wrong (and I just found out through this site), the scannner is great! I originally tried to find a free program, but purchasing a reasonably priced one really was the way to go. (I'm not very scanner literate)
I second the recommendation of ARC246...Great piece of software and it is worth every penny
However if you for whatever reason cannot afford ARC246 then go to the following site: http://home.comcast.net/~kilowattradio/ftp/
Another good (and free) software program for the 246...not as good as ARC246 but not bad either...
Hope this helps!
Marshall KE4ZNR