Recording does put additional strain on your system. I suggest trying a program like hypercam, and running the program windowed if possible. It has a good variety of codecs and you have quite a bit of customization for most of them.

more like CRAPS

What kind of a processor do you have?

Most the work needed to both display and record the content is done by the CPU. Try toying with different codecs, and trying them all at low levels of compression. You could even try no compression which would mean massive filesize, but you could just convert the video after you finish capturing it.

You want to capture at about 320x240 resolution, at 24-30 fps. If you're in full screen, run in as small a resolution as possible.

Close out of any unnecessary programs that could be taking up CPU time. You could even try  setting the priority of the recording app (fraps/hypercam) to highest in windows task manager (alt-ctrl-del).

also in fraps there's an option to select framerate. so if you set that option to a low fps, the game will run at that fps.

Try at 30 fps, thats the fastest that most video plays at.

rpg maker is 320x240 so its pretty much on the lowest resolution.
Aten as far as your problem goes, does the frame rate drop in game or on the title screen (when recording)? If you arent getting a frame rate drop on the title screen then it means that its your game causing the lag, and the video card combined with lack of ram wont help.
 

Video card and RAM are not what is slowing him down, it's his CPU alone.

Even 24 fps would be smooth enough - that's what DVD videos run at (but they have a healthy dose of motion blur).