Speakers all plugged in, audio devices detected, still no sound

was working fine, then suddenly stopped working for no reason, new speakers also do not work, old headphones that worked literally seconds before trying out new speakers no longer work.

what... the... hell...

I'm using a Dell dimension 8400, Usb headphones and speakers, tried both front and rear ports, speakers have headphone like jack in addition to Usb, tried plugging in with EVERY combination and order in both front and rear ports even one in front and one in rear, using only usb or jack, usb AND jack, usb in rear and jack in front, usb in front and jack in rear etc, etc, etc...