LabVIEW uses Multi-Byte strings, which as I understand it means that there are just more values available to a string. So for example if "A" is value 65 then you may have another language character as 400. Notice I said that another langueage, because it is not specific to any language.
When the character is going to be displayed a lookup table is used to know what image matches the character. So when you set windows up to use Chinese then you will see a chinese character, now if you change windows to another language those characters will be displayed instead. In either case the english characters should show up fine, because the bottom byte of the look up tables hold the English characters.
Here is a link to a KB that discusses this a little
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Does LabVIEW 6 Offer Multilingual Support?