Dell Inspiron 6000 dual monitor choppiness?

[Superfluous Man]

I recently hooked up my 2001FP to my Dell Inspiron 6000 to dual monitor. It started running very choppy, so much so that I had to restart the damn thing. This could be because I was running the laptop for several days without rebooting it. And it seems to be running better after a reboot, though I have much fewer programs running at the moment.

Anyway, could this problem be caused by having the laptop monitor running at 1920x1200 and the FP at 1600x1200? That is, will I get better performance by setting the laptop display to 1600x1200 when I'm using a dual-monitor setup?

Also, I got the lowest-end video card that came with the Inspiron 6000, which is the 64 MB one. Am I screwed here because there isn't enough video RAM to run two monitors smoothly? Should I upgrade it to the 128 MB model? I mean, that sounds damn expensive.