Your best options for a home use ip-pbx to run on windows are:
- Brekeke Ondo - sip server (free for home use) and ip-pbx (1 month trial, 10 user lisence relatvely cheap). You can use ip phones such as the cisco 7960, etc and softphone such as the x-ten.
- Ahead SIPSTARR ip pbx - trial download for free, you can use their SIPPS client trial download softphone and buy it for EUR 19 each, though not too much support for ip phones.
- SNOM4S - trial download available, support for both softphones and ip phones.
- mysip.ch from Siemens has some software but I have not been able to take a close look at it.
I think that this should give you some alternatives. The Brekeke ondo sip server and ip pxs are configured with explorer, so relatively easy to maintain and has a good support site in case you have configuration problems.
I hope this helps, let me know if you require additional input.