What capture software are you using? The website link I posted does have an update for Vista compatibility with their MotionDV Studio software, so it should work up to Vista. Did you install and update it? What happens when you start the program? Did you try WMM instead?
The more information you provide, the easier it is to help you. Like the absence of a firewire port on your computer, which I can only assume means you haven't tried connecting it that way, even though it is the best and most preferred way to connect a dvcam (they were designed that way).
Read pg 55-58 of your manual carefully - options have to be set on the camera to use either the usb mode or the dv mode. You may have better luck with one or the other, or with MotionDV or WMM, but you'll need to set the correct options on the camera. Actually, read everything in your manual carefully from pages 51-60, but 55-58 really explains the options you have to set for connection by either usb or firewire. If those options aren't set correctly, it won't work.
Even a little googling revealed that people were using their DV port with WMM in XP, so you should be able to do the same in W7.
Personally, I'd try it out on a computer that has firewire, and then spend $20 on a firewire card if it worked. It is the best way to work with video. USB will be slow, and analog will look like shite. So unless you are happy with either of those results, that should be your first test. Frankly, I'm perplexed that your computer doesn't have a firewire port already, either the fullsize or mini version. And yes, their are two different sizes, and you can get an adapter to go from one to the other, in case you missed that.
Hope you get it working.