Hi Yi ,

Thank you for posting your concern's here.

Have you tried reinstalling your AVG software?

If not, please reinstall your AVG program to fix the issue.

Here's how:

We recommend reinstalling your AVG by downloading the latest version from the link below:

http://www.avg.com/t...

Instructions:

1. Please uninstall the version of AVG you currently have installed.

(Start > Settings > Control Panel > Add or Remove Programs > PCReviver > Remove)

2. Download and install the software from the link specified above.

3. Please make sure you do not have any other programs/services running in the background.

4. Open the your AVG program and follow the activation procedure.

5. You will now be able to scan your computer using your AVG program.

I hope this helps!

If you have any other questions, please let me know.

Sincerely,

Christian

Hi Yi,

Let me tell you that once you have changed your Operating System (in this case downgraded to Windows 7) you need to remove the traces of AVG from your PC and then install AVG back in your PC.

You can have a repair done on your AVG antivirus using the Repair tool.

To repair your AVG please follow below steps:

1. Go to Start -> Control Panel.
2. Open (Programs) -> Programs and Features, or Add or Remove Programs.
3. Select AVG in the list of programs.
4. Click the Change or Change/Remove button.
5. Select Repair.
6. Follow the instructions on your screen to complete the installation.
7. Restart your computer.

Still if you are not able to open AVG, then use AVG Remover. It eliminates all the parts of your AVG installation from your computer, including registry items, installation files, user files, etc.

AVG Remover is the last option to be used in case the AVG uninstall / repair installation process has failed repeatedly.

The link below will lead you to the AVG Remover Tool:
AVG Remover http://www.avg.com/us-en/utilitiesThen you can have a fresh installation of AVG:

1. Click the name of your product to download the installation file:
2. AVG AntiVirus
   AVG Internet Security
3. Run the downloaded file to start the installation process.
4. Follow the instructions on your screen.
5. When prompted, enter your AVG license number. The license number is sent automatically to your e-mail once purchased.
6. Complete the installation and restart your computer.

I hope this helps in getting back AVG to work normally.

Regards,
Lokesh