I note that a common subject here is the problem of USB wireless mice not being recognized by computers. For what it's worth the following is my experience. This evening my 3 year old Logitech wireless mouse just stopped working, abruptly, and I started getting repeated messages of an unknown USB device even with nothing attached. I tried the mouse on two other computers...it worked fine. I tried a system restore from yesterday with no results. I followed the advice offered on other threads to delete USB ports and reboot...no go. Still weird behavior. I noted that one person with a similar problem turned off notebook and removed and reinstalled battery...whalla! It works. The mouse now functions and no more strange messages. I have Vista Home Premium 64 bit on a Sony Vaio notebook.