I read on one of the pages while "Converting my Server into a Workstation", that Server 2008 was only available on x64. This made me take notice as mine is on x86. Wikipedia provided an explanation, Server 2008 R2 removed support for x86, however mine DID receive the R2 update.
If it's x86, it's Server 2008, not Server 2008 R2. Those are two separate operating systems (server counterparts to Vista and 7, respectively), and you cannot upgrade the former to the latter via Windows Update, which it sounds like you're talking about. Also, if your Server 2008 version is x86, then you cannot upgrade it to R2 at all, since a 32-bit OS cannot be upgraded to a 64-bit one, you need to do a clean install instead.