512MB for video-editing?! No way. I have to use 1GB and a P-M 750 just for image editing. And a 1.6 Turion doesn't exactly bode well either. Given your demanding usage (video ed is very demanding on RAM and HDD capacity) I think you would be better off buying a desktop and even then, you should probably expect to require a RAM upgrade. At your price range, the gap between the two forms is greater.
(For video ed, I use my desktop - P4 640, 2GB RAM).