If it's not the drivers for the sound card, it's going to be hardware. But you said "I reinstalled the drivers,etc that came with the computer, then Windows updated some of those". That's a red flag because it's a very good way to end up with a problem like you have. If you want the problem fixed, the first thing to do is to replace those drivers with those you get from Dell and nowhere else.
Ok, I should clarify. When I bought the computer, it came with Win 7 Home Premium - I replaced that with a retail version of Win7 Ultimate. When I did the reinstall I used the driver disk that came with the computer for the system drivers and the onboard sound. I used the Creative disk for the sound card drivers. Window update did some updates but truthfully I am not sure which drivers it replaced. I am very ill and facing a very high risk surgery and it took all I could do to re-install, but was having major probs so I had to do it cause I depend on the computer to pay my bills, etc. It appreared to install fine, but no windows sounds. I didn't think much about it until I got my software reinstalled and discovered I had no other sounds either. Sorry, but my thinking and reasoning is not doing too well these days. I guess I will just have to call Dell unless someone can tell me how to check out why there are no Windows sounds. Also, I know there needed to be a chipset driver, but on the disk I could not find a driver that fit that. I even went back and reinstalled all those drivers, but still no sound. Thanks for trying to help.