Norton Antivirus 2009

Does anyone know if there is a workaround to install Antivirus 2009 on top of Grisoft 7.5 free edition (AVG)?  I am getting the message saying that Grisoft 7.5 is not compatible with Norton Antivirus 2009 when in fact my old version was running quite well on top of grisoft 7.5 (AVG).

 

I tried installing in safemode but it still found the grisoft product.

 

Thank you.