We use SIP at work using Windows Messenger 5.1 (still, I know) for our Windows XP clients, and there is a work around to get it to work in Win 6 64 bit (drop riched20.dll into the folder in program files). But I was also looking for a 3rd party application that is newer that would also work.
Not sure if anyone has run into this and we are just starting to push out Win 7, 64 bit at the company I work for. I know you can use MS Office Communicator, but cheapest license we've seen is about $42 per machine.
Anyone have any ideas or are using another piece of software for this?