KM636 isn't bluetooth they are linked at the factory.  Logitech K800 with Unifying adapter is the better way to go. Easily pair with other Logitech devices through a single Unifying USB receiver. Look for orange "unifying" icon for compatible devices. [IMAGE] Adding Logitech M510 Wireless mouse later is easy. Logitech Unifying Software [URL] M510 Mouse[URL] K800 Keyboard [URL]  
So  yes,  i  have lost  the  dongle. I  have  tried  the  universal  receiver  from  the KM636, also   a logitech unify receiver  but no  luck with  either. i  cannot  even find the   keyboard/mouse  hardware  on the dell site, so possibly  i  need to  use some sort  of  software   to  join with the logitech receiver? what do i  actually need as  a  replacement? thanks
REPLACEMENT DONGLE WK636 WIRELESS KEYBOARD AND MOUSE