I'm going to take the MCDST test over the Vista based one currently - on the grounds that we use XP, not Vista and will for a little while...
However, I have been wondering, is the test updated for Office 2003 and Internet Explorer 7? I used a friends practice tests and failed poorly in the second exam due to superiorly lacking knowledge of Internet Explorer 6 and Office XP
Lithium - to the best of my knowledge, it is still IE6 that is included in the exam. As for the Office part, I'm not sure which practise test you have been using but the DST has never covered Office XP - it's been 2003 from day one.
Best advice I can give you is to go through every menu in the major office apps and IE6/7 and get to know what options are available. Know how to customise toolbars, where things are in the Options menus, etc. Also, take a look at Techexams.net as they have some good resources for the MS exams.
Also, I'm teaching a DST course at the end of the month, so if I remember, I'll check with the students after they sit the exams as to whether there were any IE7 questions in there.
Awesome, thanks for the info. :)