If this means the computer will not load Windows normally try booting into Safe Mode.
Restart the computer and just before Windows begins to load, start pressing the F8 key gently once a second. After a short while the black screen will display a list of "Safe Mode" options with the first being Safe Mode itself. That should be highlighted but if not use the arrow keys to highlight it, then press the Enter key on the keyboard.
If this works Windows will load into a diagnostic mode, ie no Desktop images, lower screen resolution and larger icons. I would first see if that alone fixes the problem by then rebooting back into normal mode.
If not, restart again into the Safe Mode and try a System Restore to restore your computer back to where it was before you attempted to install AVG.
I was installing AVG 2011 free version on a computer running Windows XP. At the end of the installation was prompted to restart my computer. I restarted the computer and received this error:
AVG Installer - Error
A system restart is required in order to continue with the installation. Please restart your system and try again.
I get this error each time I restart and cannot get past it. How should I proceed?