have u checked to see if there is an available update to ur sound driver thru microsoft ..... and is it possible u have auto updates set to on and u were afk while it did an update ..... because ive had some updates cause fualt where u have to uninstal the update and then redo it from the microsoft site ..... but again this is just somthing that happened in my case ... maybe it will be of use to u to check into this also
