Right after I finished my previous blog post I started to install Vista SP1 myself. Unfortunately right after executing the installer I got a nice little messagebox, saying Vista Service Pack 1 setup couldn’t continue, because my version of Vista was unsupported. Now I run the English language version of Vista Ultimate (32 bit), so at first I couldn’t figure out why I got this error.

Then I looked at the error message more closely (unfortunately I cannot remember the exact words anymore) and noticed it said something about unsupported language packs being installed on the system (Vista SP1 is currently only available for the English, French, German, Japanese and Spanish language versions of Vista). I did remember seeing several language pack updates appear during a Windows Update session way back when I first installed Vista on this machine. However I couldn’t remember installing any of them.

To be sure I checked the Vista installed Programs and Features list for any installed language packs, but couldn’t find any. Using Google I found this article about Vista Language Packs and at the bottom of this article there were some instructions on how to remove a Vista language pack. It turned out installed Vista language packs aren’t listed in the Programs and Features list, but at a different location.

To cut a long story short, it turned out I had once installed the Dutch Vista language pack and had forgotten all about it. Unfortunately the mere presence of this Dutch language pack blocked the whole Vista SP1 installation! So I quickly uninstalled the language pack, which solved my problem.

For those interested, here are the instructions for uninstalling a Vista language pack:

1. Click Start, and then click Control Panel.
2. In Control Panel, click Clock, Language, and Region, click Regional and Language Options, and then click Change display language.
3. On the Keyboard and Languages tab, click Install/uninstall languages under Display language.  If you are prompted for an administrator password or for confirmation, type the password, or click Continue.
4. In Choose to install or remove languages, click Remove languages. 
   Under Select the languages that you want to remove, select the language that you want to remove, and then click Next.
5. Click the language that you want to remove, and then click Remove.