It really depends on what your editing software is, some are more memory hungry than others. I edit with Sony's Vegas video. My PC work fine for all the editing but when it comes time to render the final product my processor is soooooo slow. It is an older system with a 1.6mghz processor 512mb ram. It's fine for home but we have an AVID & final cut pro system at my office and they are screemers.

Ram: 512mb min 1 gig is best
Processor: As fast as you can afford
video card with its own memory 1 gig is min for editing anymore.
Hard Drive: make sure your operating system is on a different drive than your media clips

I have a 80 gig for a my Win/program files, a 120gig as drive 2 and I have a 300 gig in a portable usb case