Error message when uninstalling AVG

I've tried to upgrade to the newest version of AVG anti-virus software and in requires me to uninstall the previous version. When I try to remove the software through the add/remove software I get a Windows error message that says C:\Windows\System32\autoexec.nt - "The system file is not suitable for running MS-DOS and Microsoft Windows application. Choose close to terminate the application." I'm running Windows XP with the most recent service pack installed. Any suggestions?

 

Try going to program files, AVG and use the AVG uninstall.

 

Are you upgrading from 6.0 to 7.0 (Free version)? If so, you may want to see this:
http://free.grisoft.com/doc/5468/lng/us/tpl/V5

 

http://support.microsoft.com/default.aspx?scid=kb;en-us;324767

step 4