I have beed working on this same issue with my Cell phone. I have a Kyocera 7535 SmartPhone. What I did was connect the Data Cable to my PC's USB port, configured the phone as a modem then I purchased a APP called Communicate (Actually I have had the app for a long time). What the app does is it acts licke a personal communication center. You can configure the app to do what ever actions you want when a phone call comes in (IE recieve fax, go to answering machine or display an answer box or drop popup window.) You can set your own ringtones for incoming calls and as an added bonus it pauses any video and or mp3 player and lowers the volumes so you can recieve the call. There are a few bugs. The app can get very dificult to use with a touch screen LCD. I have had situatuions where once i took a call that I had a hell of a time closing the app windows. Also, I am running Windows XP embedded and the app is a pig when you are playing video and tring to recieve a call. It could take 3 rings before the answer call window pops up. I used to have it on a full version of XP and it worked great. Also, the caller ID function works when it wants too. But, even with all those issues it is a good solution for your problem. I am working on creating my own app to do the same taks but it is taking a bit longer to write. There are also lots more apps that can accomplish the same thing I just wanted to only spend the bear min. on this part and didnt want to end up purchasing tons of software to just test if it will work right.
Hope this has hellped.