Multi-language should be in all versions.
Too right it should - ideally, it should have been in Windows from version 1 onwards, but when Windows was written I don't suppose anyone thought about it.
The concept is called 'localisation' today and is (or should be) considered at the earliest stage of design of a software product if the product is needed to be multilingual. In fact, it must be considered at this stage, because building it in as an afterthought is going to involve - effectively - starting again from scratch.
Don't think that it's a simple thing to do. Of course, you can go through the source code and replace every string literal with an index into a Text_Strings array, then initialise the indexed array element with the original text, to produce an en-us version (assuming that was the original language). To produce a German version of the program, you just need a German version of the Text_Strings array.
Unfortunately, German is a somewhat more verbose language than English, and many of the resulting text strings will be longer than the originals. The screen space needed to display them will therefore also need to be larger. The designers therefore need to revisit every message box, dialog etc. to make sure that the message is viewable in every supported language, including those that are written vertically.
And that's just the beginning. Consider this line of C:
displaystring = sprintf("Agent number "%n" has "%n" clients, and generated "%n" percent of our business", agnum, GetNumClients(agnum), .... );
In English, this will produce a string that makes sense, but other languages have different syntax and different grammar, and it isn't possible to produce meaningful output from this code in Hungarian, for example, just by replacing the string literals. This line of code, and probably many others, needs to be rewritten to construct meaningful sentences depending on the target language.
So in conclusion, Microsoft could have produced a language-neutral version of their OS long ago, but it might have cost them more than producing multiple versions.
The odd thing is that it's only available in (I think) Windows 7 Ultimate Edition, although, as I explain above, it requires a complete redesign of of the OS. I suggest that it's also in other other versions of Windows 7, but the installation of other language packs is disabled.