Lets see, can you expound on what kind of video/ graphics (pic) editing you'll be doing? Will you be surfing the web while editing ... lets say 25 pictures using photoshop? I do this routinely with a 755MHz/ 256mb ram laptop and it works just fine. Video editing is certainly going to make your machine more RAM and CPU hungry.
I'd say that 512mb RAM should be the minimum if your going to do any type of video/graphics editing as some of those programs just don't do too well without that much. Also, you might pop into a local apple store and try to do web surfing/word/graphics editing all at the same time. I only notice severe lag when I have three or four hungry apps open at the same time.
Aside from video editing, I think that 800mhz would be the minimum I'd settle for. For more extensive video editing, I'd get the fastest processor I could afford. Ram, I'd say that only under extreme circumstances would I accept 256mb RAM (otherwise your constantly paging). 512 should be the defacto minimum when video/graphic work is on your plate. I've worked comfortibly on a 30gig HD for a couple years, but I'm also not installing a lot of new stuff-nor am I using my laptop for gaming. Burning to CD is a great way to store rarely used files when you lack HD space.
Finally, used or refurb? I've used a refurb for about 6 or so years and I'd say it has no more problems than any new laptop. I wouldn't buy a used laptop or PC. Laptops are notorious for taking more physical wear and tear (READ: abuse) than PCs, and seem to pose more risk to the buyer. If you could buy a certified pre-owned, that would be the next best thing to try. Hope this helps.
