Increasing the ram is right on target. One thing that you can try is to keep the processor from throttling down while on battery power. The processors on notebooks will slow down to conserve battery life at the expense of speed. Right click on "My Computer" and select properties. From there look at the listing for the processor speed/rating. Below that the actual speed of the processor will be displayed next to the RAM. My Lenovo thinkpad has a utility to adjust this setting, I am not sure how is it done through the windows interface. This may or may not help much. AC is not that demanding of a program.
Another issue is that these laptops are bundled with junkware. I have had to clean up and tune a lot of this thinkpad that I have to make is work well. It is fresh out of the box x61 tablet but the performance in WinXP sucked. I had to use MSConfig and services.msc to clean up the junk.
