Hello and welcome,
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 beside it
3. The manufacturer name and model number of your PC, if applicable
4 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.
The exact make and model of your motherboard and video card would be of great help also, so we can try to locate Windows 7 drivers for your video card.
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?