Windows 2K3 Server Enterprise

experienced people in Windows 2003 Server edition then me.

Now working for this client of mine seems they have much more problems then just a single hard drive issues as posted in another post.

Now they also have a Windows 2003 Server Enterprise Edition on their server, which is activated but their Product Key fails every time they try getting an update like SP1, etc...

Now, I'm guessing it's because their product key isn't the original or fake as they never purchased Windows 2003 but the tech they fired installed it any ways and got it working.

So I went out and purchased an Windows 2003 Server Enterprise Edition (OEM Version) as it's cheaper and I had to build a system recently so that worked out pretty well.

Anyways, using all of the tips on the internet to disable or deactivate windows worked well but when using the Activation Wizard and entering the new product key, it just comes back to the product key area again. So I've called Microsoft and the guy on the phone wasnt able to help me nor activate the windows.

Question:

Does anyone here have experience with Windows 2003 Server and would know why this is happening or know a fix?

Do I have to reinstall the OS?

If reinstalling, can I do it the same way as Windows XP that you select to install a new operating system, then select the partition, it detects the operating system on there and replaces the OS files only with the new ones but leaves everything in the same state, does something like this work or is available in Windows 2003 Server?