Sorry for all the questions, but........
In order to troubleshoot your problem we need to know more detailed specs of your system hardware.
1. Go to Start > Run, and type msinfo32, look under the Components
section for hardware identification
2. Go to Control Panel > Device Manager and look for any entry that has a yellow flag
3. The manufacturer name and model number of your PC, if applicable
4. Download [URL="http://www.majorgeeks.com/SIV_System_Information_Viewer_d4779.html"]]SIV (System Information Viewer) 4.00
for very detailed information about your system.
5. Or PC Wizard 2009.1.88
6. Please fill out your computers specs in the User Control Panel here on the site as well. It will then appear next to your name. look at my posting and you'll see the drop-down arrow.
make and model of your motherboard and sound card would be of great help also.
Are you using the 32-bit or 64-bit version?
Was it a "clean" install or an upgrade?
Are you dual-booting?
Are you using the official RC directly from Microsoft?
Did this occur immediately after install?
Do you recall installing any software that may have caused the problem?
There are many versions of the Realtek AC'97 drivers and codecs.