My computer works, except for the sound/speakers and I'm unable to reinstall printer. The yellow light at the rear of tower blinks intermittently as well.

The yellow light is probably simply your NIC card transmitting data, and is not to be worried about. As for your driver issues you need to simply look up your PC model(if prebuilt) ex dell optiplex(model number) etc on the manufactures website and select the needed drivers(in this case sound card) and download and install. Same for your printer. Ex hp laserjet xxxx which can be found on the manufacture of your printers website.