Since you are running Win7 on a Mac Mini, you are stuck using Windows 7's built-in bluetooth support. It is pretty basic and has no built-in support for the A2DP profile (Microsoft left it up to the bluetooth manufacturers to provide support for more advanced profiles like A2DP). I'm assuming that it doesn't work under OSX, either? I know little about OSX, but I dimly recall reading somewhere that the Mac hardware is fully capable of supporting bluetooth headsets and A2DP but that it doesn't have software support yet in OSX.
What happens when you try to pair the headset with the computer in Windows 7? You have to set the headset to discoverable mode (
http://ars.samsung.com/customer/usa...PG_ID=0&AT_ID=96045&PROD_SUB_ID=0&PROD_ID=786 ). Once you have done this, you'll then need to run the bluetooth connection wizard in Win7 to search for the headset (
http://windows.microsoft.com/en-US/windows7/Add-a-Bluetooth-enabled-device-to-your-computer ). Once it is found, you'll have to enter the pair code (should be 0000). You'd go through a similar process in OSX.
If you can't connect it as a stereo headset, try to connect the headset as a mono headset. If you get it connected, check windows update with the bluetooth headset connected to see if any new drivers are downloaded.
If you can't get it to work, you'll likely have to invest in a bluetooth dongle that comes with a driver supporting headsets. Make sure to read the description to ensure that the dongle supports headsets/A2DP as a lot of the cheaper ones don't (like the ultra-cheap ones at DealExtreme or Monoprice, etc).