Sound stopped working after Vista update

I have Windows Vista installed on my machine and recently it downloaded the critical update and installed it, but soon after that this system used to crash with blue screen error messages. But later when I started my pc after 3 days then it again started to install some new updates and when it was done, the sound was not working anymore. So i tried to uninstall the driver for the sound in Device Manager and when I tried to reinstall it again then it gave me an I/O error and the installation used to fail. I have done this many times but it will still give the same error. This is an HP pavilion laptop and it has a Realtek HD Audio onboard. Can anyone help.

This same thing was happening with my computer. But later on when I installed service pack 1 of Windows Vista then the default sound device changed from my sound card to my usb sound device that was skype phone actually. Then I went into control panel >> sound >> playback tab and selected the default playback sound device and then everything started to work fine like before. Hope that this info will help you out as well.