If you are still stuck on the IIS section, here is how to do it:
Start > Control Panel > Administrative Tools > Internet Information Services (IIS) Manager
For me, there are two IIS managers, one is 6.0 and one does not have any version declaration. I use the latter, the 6.0 does not bring any information up.
Once you have the right manager open, you should see your computer name on the left side in a tree view. If you expand it, then expand Sites, you should see "Default Web Site". Expand that and find your SiteFinity installation. Right click on it, mouse over "Manage Application", and then select "Advanced Settings". You will get a dialog box, on the top you will see "Applications Pool", and DefaultAppPool should be its value. Click on it, select the button with the ellipses in it (...) then change the drop down value to "Classic .NET AppPool"
Hope this helps!