i just can't get which virus infected my computer

whenever i insert my pen-drive, its displays new hardware found continuously even the installation process for the new hardware is finished, still it pops the yellow balloon showing new hardware found... to use my any how i can use the usb-drive ignoring the messages and killing some process like hkcmd.exe, cfmon... help i can't guess which virus ruled my pc. i've avira premium edition installed to my computer...