Hi,
Strange - I'm running Vista and the latest version of BeerSmith now and you can enter anything down to 0.01 as the unit price - I just veritifed this in Shopping view.
Just to double check - go to the Vista control panel, click on "Clock, Language and Region" selection, then on the next page click on "Regional and Language options". Make sure you have the Current Format under Formats tab set to English(United States), and also the Location set to "United States". These locale settings are used to generate the number formats under BeerSmith.
Looking at the code, it appears this gets reset every time you enter the program, so if the windows locale is OK, it should reset these options and display correctly.
Sincerely,
Brad