Upgrade Windows 2008 Standard to 2008 Enterprise

I've recently needed to upgrade Windows Server 2008 Standard Edition to Server 2008 Enterprise Edition to take advantage of additional memory on the server. I'm running the 32 bit version OS not the 64 bit. The 32 bit of Windows 2008 Standard only supports up to 4 GB of memory but the Enterprise Edition will handle up to 64 GB. (memory limits MSDN)  All the documentation I could find (blog posts, MSDN, TechEd, etc) suggested that the upgrade could be done in place but that there were some considerations depending on certain roles the server plays.  Fortunately my server didn't fall into any of those special circumstances.  However, when I ran the install and selected Enterprise Edition I received the message:

"Upgrade has been disabled.
The upgrade can not be started.  To upgrade, cancel the installation and then choose to upgrade to a version of Windows that is more recent than the version you are currently running."

and the button I would use to perform the upgrade in place was disabled.  Naturally I was a bit confused since my current installation was Windows 2008 Standard Edition SP2 and I'm trying to upgrade from Enterprise Edition 2008 SP2.

After a bit more digging on Google I found this blog post (Thanks Network Steve) that suggested that maybe SP2 was the issue causing the button to be disabled. So, not feeling very good about this approach, but with no other real options, I decided to go for it.  After making all the necessary backups I uninstalled the service pack. Yes, the OS still booted and seemed to work and fortunately for me this actually solved the issue with the installer.  I was able to do the upgrade in place from Standard to Enterprise Edition.

Hope this helps someone else!