Change asp.net version in IIS 7
1. Login with remote desktop and open Internet Information Services on the windows 2008 server. This is found under Start Menu, Control Panel, Administrative Tools, Internet Information Services (IIS) Manager.
2. Click on the + next to your server name and then click on Application Pools.
3. Locate the application pool for the website you are changing asp.net for. Right click on the application pool and click on Basic Settings.
4. From the drop down menu under .NET Framework Version choose the version of asp.net you wish the site to run on. If asp.net 1.x or any other version you wish to use does not appear it will need to be installed.
You can download different versions of asp.net from Microsoft's website or you can contact GearHost to install this for you.