This is for a Vostro 1720 Vista 64 but it will work. LINK This is from the Inspiron 1545 for the Bluetooth 365 Windows 7 x64 and should also work LINK. This is from Studio 1555 for the Bluetooth 370 Windows 7 x64 and should also work LINK. It has been a while since I had to download the driver that I do not remember which one it was for sure. Any of the ones that I linked to should work just fine. For some reason I am thinking that with the Beta I used the first driver I linked to but I may have just let windows install it with the RTM that I am running now.  
Got a problem: Upgraded my 1720 on Win 7-64bit changing from Vista-32. Unfortunately it seems that my support stucks with Vista 32 and though the system runs much better than it did with Vista I still miss the Bluetooth device and seek to get an appropiate driver. Any idea? Quite awkward that Dell does not give me a choice for a OS-system in terms of choosing a recommended OS!! I would appreciate any help may it only be a suggestion on who is the manufacturer of a "Dell Wireless 355 Bluetooth 2.0 Module". Thanks for help!
Inspiron 1720 Bluetooth driver for Win 7 64bit