Can't uninstall AVG antivirus to reinstall

Ok, Hope I'm in the right place. I call my self befungled because I am. I'm computer clueless but can't afford to just take this to a shop so must try to sort things out myself. I hope to update the system this coming year but want to keep this one going til then. I'm on Windows 98 and have AVG free Antivirus. It got messed up and won't update. I tried to reinstall but it won't untill I uninstall. I can't uninstall because (error message) Local machine: installation failed Installation: Error: Action failed for file setup.exe: creating backup…. Access is denied. (5) %DESTINATION% = "C:\Program Files\Grisoft\AVG Free\setup.exe.install_backup", %SOURCE% = "C:\Program Files\Grisoft\AVG Free\setup.exe" I'm also pretty certain I have a bug in my c'puter's guts. Help most heartily desired and appreciated!

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