Is the bluetooth indicator lit up?
It's located above the keyboard on the right side, between the WiFi and hard drive indicators.
Fn+F2 is the usual Dell hot-key combination to toggle WiFi and/or BT (typically definable in QuickSet).
There IS a driver update available for it
http://support.dell.com/support/downloads/download.aspx?c=us&cs=04&s=bsd&releaseid=R204794&SystemID=STUDIO1537&os=WLH&osl=en&deviceid=19472&typecnt=0&libid=5&fileid=286034But it's only 'recommended' - if its status was 'urgent' it might be needed to make the BT work at all.