It isn't really as clear-cut a case as "older version = less graphically intensive." While the older MediaVPs did have fewer graphical enhancements (due largely to the fact that fewer models/effects had been worked on back then), those they did have were often significantly less efficient than their counterparts now, and the arrangement of the VPs meant that certain high-impact effects were located amongst less memory-intensive options, where they didn't belong. In addition, I doubt that the previous MediaVP set would play very nice with recent builds, and the last thing you want to do is use previous SCP releases. If your rig can't handle the 3.6.10 VPs, I doubt you'd have any better luck with what came before.
On a slightly different note, if you knew what sort of motherboard was in that machine and what it supported, you might be able to find a cheap graphics card that would still be a big boost over what you have now. If you download and run
CPU-Z (just the no-install 32-bit version should be fine), run it, and click "Save Report" on the "About" tab, you should be able to generate a profile of your system hardware that will let some of the hardware gurus around here determine what your options are.
(Also, I'm going to move this over to Support, since it probably belongs there at this point.)
