First check in your BIOS to make sure on-board sound didn't get disabled.
Next try:
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Download a 'live CD' version of knoppix or ubuntu or similar and burn it to a CD.
- These are Linux based operating systems that you don't have to install to run.
- They will work right from the CD without altering your hard drive at all. (Unless you want them to.)
Change boot order in BIOS to boot from the CD.
Do it.
See if the sound works now.
If yes - Sound problem is Windows based.
If no - Sound problem is a hardware problem.
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If it's a windows problem remove and reinstall the drivers. (From within Windows of course.)
Driver may simply have gotten corrupt.
If it's a hardware problem get an add-in sound card or one of those USB sound gadgets.
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