The PC does recognise my Logitech USB 'Trackball' mouse, and it 'sees' the LI-USB but that has the yellow mark on the icon. Further investigation (Or in my case, much blundering about and cursing!) reveals that "Windows cannot find the driver". I've tried the 'look on the internet for suitable drivers' option, no joy, also tried the 'look on the computer' option but again, despite having unzipped and installed the updated (V3.6) drivers, Windows can't find them. Shame there isn't a 'Try Specsavers' option! Trying another tack, last night I was fortunate enough (I hope!) to acquire a Lenz 23151 LAN/USB unit on Ebay, complete with leads and CD for £100 (New these are £165) so I am hoping that this may be the answer rather than spending the rest of my days literally banging my head against a wall in trying to get the 23150 unit to work for me, as I have better things to do with my time (and models to build/complete!). Once that arrives, I may well be back with more daft questions, so "Watch this space!" In the meantime, many thanks for all your help and suggestions, you have no idea how much I appreciate them. Keith.