Non-existent USB device installs repeatedly

[Pawnless Endgame]

All USB devices are currently unplugged (even going back to PS/2 keyboard atm). Despite this, something installs itself, comes up with "USB device not recognized" in a bubble by the clock, disappears, then comes back. Repeat >20 times in the time it took me to write this. You hear the ding-dings as well. I don't think it's a faulty port because I inserted a USB stick which came up fine on all ports. Just using mobo ports for now. Front ports/sound jack connector is currently disconnected. No card reader present. Any ideas before I lose my sanity?!

 

[Pawnless Endgame]

Thanks for the suggestions.

- no WLAN devices present
- turned PC off/on to no avail
- have checked ports, bit of dust but no arachnids as far as I know

Here's something interesting though: the motherboard only has 4 USB ports but in Device Manager, "USB Root Hub" is showing up as having 10 ports.

When I plug a USB stick into ports 1, 2, 3 or 4, the location shows up as Port_#0001.Hub_#0001, Port_#0002.Hub_#0001, Port_#0003.Hub_#0001, Port_#0004.Hub_#0001 respectively. However! The offending non-existent device shows up as Port_#0005.Hub_#0001... USB port 5! Where the hell in my computer is that? Or are 5-10 'logical' location as opposed to physical? If that's the case, how can I disable these ports and thus prevent the message from keep popping?

 

[Pawnless Endgame]

Thanks again guys!

Regarding USB headers, I thought the thing was usually soldered onto the board? 4 ports arranged in a 2x2 block and it looks fairly firmly seated when looking inside the case. The front 2 ports does have a header though and is currently disconnected in process of elimination.

Will have a look at chipset drivers though, last time checked being back in July.

P.S. had Microsoft Security Essentials as realtime scanner since day 1 to rule out virus activity. Windows 7 Home 64-bit.