When i run my site the webform isn't going into the code behind side script at all

It seems like the older version RSProj2008.dll file is referenced in GAC, how to completely uninstall older version from clients server and reinstall fresh. i uninstalled but still the virtual folder remainin and not allowing me to delete the contents keep getting message file write protected or someone is using.
<%@ Page Language="vb" AutoEventWireup="false" CodeBehind="PrintLabel1.aspx.vb" Inherits="RSProj2008.PrintLabel" %>

Thanks a lot for the helpful info.