I would like to know if I can install IIS 7.5 on Windows Server 2008 and NOT Windows Server 2008 R2?
+1
A:
Short version: No, you cannot.
The IIS version has always been tied to the OS, there are many underlying things in the OS to support it. Keep in mind that 2008 R2 will run 32-bit programs including web applications via WoW64 if that's your aversion to upgrading to R2.
Nick Craver
2010-03-02 13:56:00