Re: NO SOUND DEVICE ?
One thing at a time.
As for the task bar problem, it is with your video card/port or your monitor. Try refreshing the monitor. If it has no setting to degauss, just disconnect the power cord for a few minutes, then reinsert. If this doesn't fix it, try to reinstall the drivers, or get new drivers from your card/board/computer manufacturer.
Is your sound card showing in Device Manager? Any sound devices showing as not installed? I would doubt your kids would know how to disable it in BIOS.