When using still images in a presentation in Vegas 7, I understand that photos should be no greater than 2k X 2k,when the final will be for an HDV DVD, but what resolution should they be when resizing the images in Photoshop. Should it be 72, 300, or something in between?
Ignore dpi as it's a photography term that bears no relation to video.
All you're concerned about is the number of pixels.
If you're doing SD video, then your screen is 720 x 480 (for NTSC.
You need to decide if and how much you want to zoom in on the image and set the sizre accordingly.
BTW, I've had images that were 5K x 5K on the timeline simply because I had to do an extreme zoom on them.
My machine struggled but it did work.