Most people on installing .NET 3.5 on the server "expect" an entry for v3.5 under the ASP.NET version Tab in IIS manager. And not finding that entry start panicking. If you have been one of those read on. The more tech savvy folks try to run aspnet_regiis...
Mike Volodarsky has post a list of breaking changes for ASP.NET 2.0 application running in integrated mode on IIS 7.0 read them here http://mvolo.com/blogs/serverside/archive/2007/12/08/IIS-7.0-Breaking-Changes-ASP.NET-2.0-applications-Integrated-mode...