Yesterday I installed the first service pack for Vista. But at first I had a problem installing it. Right after starting the installer it showed a message that I did not have the right language version of Vista installed. Weird, I thought, this is the english version. The message mentioned something about incompatible language packages also, but I did not pay attention to that. Disappointed I searched the internet with Google to find out if there were other people with the same problem. There were none but one. (S)He mentioned language packages also. Hmmm, wait a minute, I thought, I installed the dutch language package. Is this the problem? Yes, it was. After uninstalling the language package the installation went fine.
How do you uninstalling a language package? In the control panel search for ‘Regional setting and language options’. Also see the figure below. Double click it and go to the ‘keyboards and Languages’ tab. In the middle of the tab you see the ‘Install/uninstall languages…’ button . After clicking it a wizard lets you select language packages to uninstall.