The software is available from any Siemens distributor, and is only in the hundreds of dollars. (I think $300 - $500???) The one thing to watch for is the Step7 microWin workis only with the S7-2xx PLCs. If you want to use any 3xx or 4xx series PLCs, you need S7 complete package that runs a few thousand dollars.
I hope this helps a bit.
Adam