Recently, we began the install of a new instance on a VMware Host and ran into an issue with a problematic outdated ISO file. Therefore, those of you embarking on new SQL 2008 installs, please avoid a potential headache, as personally exposed to (and like these guys lived through also), by simply downloading the latest ISO media/image. The following is simply an anecdote of frustration.
Our headaches began upon mounting the [outdated] SQL 2008 ISO on a Windows Server 2008 host. Once we selected the CD/DVD drive, the pop-up/dialogue box error occurs after invoking the Setup.exe:
Microsoft .Net framework 3.5 install has failed
SQL Server 2008 setup requires .Net framework 3.5 to be installed
You can use this Dot Net Framework Verifier if you are in doubt as to whether your .Net version is okay.