Don't know if this is the same for the Curve, but on my BB Bold 9780, I was told that I had to have the BB Desktop software installed on my pc.
Certainly, on my phone, if you want to say, just download photo's to the pc, you don't need the software. All I do is, once I've plugged the phone in via the USB lead to the pc, on the phone itself, I click on "USB Drive" - and then you get the standard box that pops up asking if you want to open files etc....
Then, it's just a simple case of dragging and dropping/copying and pasting...this works for transferring music/vids/pics etc from the phone and also transferring stuff to the phone...