The one I use isn't free (I use Amplitube), although there seem to be some free VST guitar amp sims around.
Any you find will most likely going to be VST plugins. If you're not familiar with them, they're a type of standard plugin that require a host program to run them in. Not sure how well these will run on a standard laptop soundcard, but you don't know until you try. A simple free one I use is called VSTHost, which I think would do the trick. Then search the Google for something like "free guitar amp vst".
Here was one of the first results to pop up. Check out some of these. I haven't tried any of them myself though.
https://freemusicsoftware.org/category/free-vst-effects-2/amp-simulatorsNot sure if there are any completely standalone solutions, but this would probably be your best bet.