Vista - Cannot install additional language packs in Vista Ultimate

Try as I might, I cannot succeed in installing two additional language packs
in Vista Ultimate (original English, LPs in Dutch and French). Invariably, I
get an error code 2, but the Microsoft sites remain remarkably silent on this
issue. The only "solution" I found was to install KB942903, but this only
resulted in a message that this "doesn't apply to my system" (Vista SP1).

Looking further, reference is made to a file LP-zh-CN.exe, which I
understand is the actual installer that gets downloaded via Windows Update
and that is supposed to be in the
c:\Windows\SoftwareDistribution\Download\Install directory. Problem is, there
is no Install directory.

I have just done a full re-install of Vista, but this didn't help, and I
still get the same error message, for both the Dutch and French language
packs.

I'm at a complete loss as to what I should do to install the additional
language packs, and wonder how else I could proceed.
--
Luc