Correct, it's all depending on how you use it. If you're in any way hinting at a software product, you might have to face the MS suits at some point. Your best bet, check
www.uspto.gov for existing TMs regarding "Vista" and then base your development or keyword selection when parking on your findings. Until then, reg.fee because of the potential dangers, once in the clear, it's going to depend on how you use it.
IB