First of all check your device in some other computer and check that there is no problem with phone and data cable as it is the better option to get secured with the phone hardware...
after checking now its time to check the computer just go to device driver and see the options what is happening over there and see what options appear there
and also scan the computer with some antivirus and try to update the motherboard drivers from the manufacturer's website it will be done...
I hope it will be done now
for further querries just mail to :
anand_nayyar@yahoo.co.in