This is not really a question but a post of a solution I found to a problem that might be useful to others. I've been using Win 7 64 bit for a few months now and its been fine - this is a Dell XPS-420. This system came with a Dell remote control and IR receiver.
For the past couple of weeks the IR receiver for the remote control has not been working - the remote itself works OK and lights up etc - no problem (obviously it doesn't do anything though). I was beginning to think some Microsoft fix had messed up the IR receiver since it used to work and I have recently had quite few device driver messages about USB devices and I could not see the IR receiver anywhere in the device manager list but I'm convinced I used to see it there. I had also noticed that the little green light which used to be lit on the IR receiver was no longer lit. I tried unplugging and re-plugging the USB cord but it made no difference.
Anyway to cut a long story short I did two things which seemed to fix my problem. First of all I accidentally discovered there is an on/off button in the top right of the Dell remote control which I had previously used to get out of Media Center - however when I pressed this button, lo and behold, the green light on the IR reciever came on (the dell remote control did not come with any documentation so I have no idea what some of the buttons on it are really supposed to do)!
However I still had to do one other thing - no matter how many times I unplugged and plugged the USB cord for the device it would not show up in device manager (although I did continue to get an unknown device not working message). So I decided to unplug it from the Belkin powered hub (where it has been for the past 2 years) and plug it into one of the onboard USB ports, and once again it all started to work, and I see a device in the HID section of Device Manager and no error devices! If anyone does have an explanation for this bizzare behaviour I'd be interested but otherwise I post this in case it helps anyone else.