Well, it's a toss. 512MB would help for vidding but it might be at the expense of an already fragile system.

In those conditions, I think you should consider encoding at half resolution with a high-end codec that won't get Premiere to crash. I find that better than encoding at full resolution with a crappy codec. Cut up your clips so that the files don't get over 200-300MB, that'll help with the RAM. If you need two different bits of the same scene, make two different clips.

And don't forget to set the auto-save project at a short interval. *g*