"Windows Vista" has not been used by another company. "Vista" is not the name of any extant operating system.
As for "mondo", it means society in all of the languages I've heard it used in. I've never heard it being used in the context of meaning "enormous" or anything similar. In Esperanto, Italian, Spanish, Ido, etc. it means "world", "kingdom", or "society." When looked at in this perspective, "Office Mondo" makes sense because it is essentially targeted at the "Office Society." It also makes sense in the way it was pointed out earlier in combination with Windows Vista (Scenic View): "See the world with Microsoft!"
I believe Office 12 was not a name at all. Office 12 is nothing more than a version number. As far as I can tell, "Office Mondo" is just a code-name. I can't imagine Microsoft using a non-English term as part of their product name because Microsoft itself is mostly an English company and its largest consumer base is English. I think it is fairly likely that "Office Mondo" will be termed with an official year-form name like we are familiar with.
I think you just disked every non-English speaking Windows user. Its also a bit contrary, the next version of their most popular product Windows is using a non-English name "Vista" which means View. Whats so different about another non-English name "Mondo" which means world? The name does not necessarily affect a products value, it is not a feature or functionality, just a name with a deep meaning to reflect what the product has to offer. Again, Microsoft does not code name a product, that already has a code name.