I haven’t been using Bluetooth on my D830 before but now I got myself a Bluetooth mouse in order to get rid of the receiver for a wireless mouse. And then I discovered that Bluetooth did not work anymore after I installed Win7.

Browsing Dell support pages for a a driver found me one (browsing by computer model etc..). But that drivers does not work. Installation looks ok and everything but no devices are found. i kept looking and found this driver, also at Dells site:

http://support.us.dell.com/support/downloads/download.aspx?c=us&l=en&s=gen&releaseid=R231570&formatcnt=1&libid=0&typeid=-1&dateid=-1&formatid=-1&fileid=333170

And that one worked! 
Problem solved an I am now happily using my Bluetooth mouse instead.