I know it's an old thread but just worked out how to do it myself and though a helpful post would be good
You need to have your bluetooth dongle ( I'm assuming you're using a usb dongle on your desktop ) plugged into your PC. This should give you a new icon in your taskbar ( down near the time in the bottom right ).
Make sure you've enabled bluetooth on your Streak ( under Wireless & Networks ) and then go into the Bluetooth Settings and make your Streak discoverable.
Now go back to your PC and double click bluetooth icon in taskbar. Click Add button, then click My device is ready to be found and click next and it should search and find your Streak. Select it and click next and then enter a passkey of your choosing. Click next and then you should get the pairing request on your Streak, enter the code and bingo they should pair.
By default they're not permanently connected. I then went to the Com Port tab on the PC and added an incoming port ( com 3 in my case but it may be different for you ).
Then to send the file from the Streak, I right click the bluetooth icon in the bottom bar and select " Receive a file ", then go to the Streak, pick my picture, select Menu, then Share, then Bluetooth, then select your device from the bluetooth devices listed ( you may only have your PC listed ) and BINGO
Your PC should pop up a window giving you the chance to rename and save the file.
Done