Dell 8300 and windows 7

It's really time for a new PC if you want to fully run Windows 7. 

There are no Dell drivers for either the sound or NIC (Vista drivers will work but Dell does not support Vista on this model).  You could disable the Integrated Audio in the BIOS and  install a PCI sound card that is compatible and a NIC card that is compatible and use those.  The audio is handled differently in Vista and Windows 7 and the reason the older XP drivers will not work.  The least expensive (and compatible) SoundBlaster sound card is the Audigy SE.

That NIC card is not listed in the Dell drivers so I assume that was an add on that you installed.  The Linksys (Cisco) site has drivers but not for Vista/Windows 7, so it will need to be replaced with a Vista/Windows 7 compatible model.  

I agree. The only systems that will handle a Windows 7 installation would be systems made in the last 2 to 2 and a half years

Thanks for the quick reply. Well that is what I thought you might say about getting a new computer. Not worth rebuilding this one.

I was having the same problem (Dell Dimension 8300 w/ recently installed Windows 7 and no sound) until I followed the advice of "Fireberd" above and replaced the original sound card with the SoundBlaster Audigy SE.  My old 8300 now has sound!!!  I also installed a Wireless-N USB Network Adapter, a new 160 GB hard drive and upped the Ram to 3 GB.  Believe me when I tell you that it works like a brand new computer.

I agree. The only systems that will handle a Windows 7 installation would be systems made in the last 2 to 2 and a half years

Not true ... I have installed Windows 7 on several older PCs, including a 2350, and it was quite usable.