PC not recognising Archos AV500 Windows Device

A couple of weeks ago I had to restore my Dell PC to factory settings because it was refusing to boot and reinstalled a few applications. Over the weekend I connected my Archos AV500 DVR to it as Windows Media Device, and instead of the 2 tones you normally get when you add a USB device, you get 3 low tones, and it will not show up on the Explorer. If I change the Archos to Hard Drive device mode it gets recognised, but the PC wants to format it and wipe all the contents, which I don't want.
In work the PC recognises the Archos in Windows Device mode no problem.
The Archos is configured to work with all XP PCs so it should work out of the box.
I downloaded drivers for it but the PC at home says it can't install them..I ran troubleshoot on all the USBs (I don't know which is which in the Device Manager/Universal Serial bus controllers) and it says there is nothing wrong. But then my main external harddrive stopped working on the same USB, and I got the 3 low tones again instead of the 2 you normally get. This morning I plugged the external hard driver into the same USB though and it was recognised again..
I read on an Archos forum that the best bet is to uninstall all the USBs and reinstall them, but I have no idea how to reinstall.. please help its doing me brain in, I need the PC to recognise my Archos again!