Place calls from Windows (7) using a SIM-card
Usually 3G USB internet modems do not provide functionality to place calls, although you may find a similar device which would enable this
Have a look at these solutions: http://www.voip-info.org/wiki/view/VOIP+GSM+Gateways
Yes, you can. I have used my Acer 1420p to make phone calls. Here is how: http://forum.notebookreview.com/acer/482532-enabling-ussd-voice-support-em770w-3g-module.html