Prior to migrating to Windows 7 from Windows XP did you run the Windows 7 Upgrade Advisor?
To determine if your current computer configuration will be compatible with Windows 7 please go to the following link: http://tinyurl.com/no4xb7
Another resource to verify compatibility is available at the Microsoft Windows 7 Compatibility Center located at the following link: http://bit.ly/1gW6Ns
Have you updated your graphics controller drivers as well and ensured that the drivers are indeed compatible with Windows 7?
Microsoft Windows Client Team