Hello hem66. I understand there is no sound on your computer, after upgrading to Windows 8. I researched this computer, and found out it was originally released with Windows XP. This would limit the amount of supported drivers, for this operating system.
For more assistance in troubleshooting your sound issue, this HP document offers suggestions you should try. If you do not have any sound, after following this document, this shows that this computer may not be able to function correctly, with Windows 8.
Let me know if you have any questions or concerns. I'm only here to help!
Mario