For a few years before I got Pro Tools, I was running the Kjaerhus Audio Classic Chorus plug-in on a Hewlett Packard Pavilion dv8000 PC lap top, and in Cubase SX 2 and 3.0. The computer had a 3.0 Ghz processor and 2 GB of RAM. I can't think of any time that I had a problem with the performance of this plug-in, as this plug-in doesn't take up too much processing power. Being that it is free, the best way to figure out if this will run on your system is to simply give it a try.
For a free modulation plug-in that is on the older side, the Kjaerhus Audio Classic Chorus actually sounds pretty good, or at least it did the job for me a number of years ago when I used to run it. I like the presets as they offer up a good showing of the versatility of this plug-in. While it may not have the pristine clarity that newer chorus plug-ins will have, it's worth downloading as a free plug-in.