Boot into Safe Mode by waiting until the memory and drive checks when the
system starts are done then either hold down the Ctrl key or tap the F8 key
several times before Windows starts.  Go into the Device Manager by
right-clicking My Computer, selecting Properties, then the Device Manager
tab; and remove all modems, all unknown or problem devices.  When you
restart the devices will be gone from Device Manager ... but the drivers
will still be there, Windows should then be able to sort the whole mess out,
usually without having to reinstall the drivers.