Here you can download a nice set of presets(settings files) that I've made specifically for a guitar. They include a nice solo guitar distortion and a pair of heavy rhythm distortion effects. You just have to plug your giutar in the mic (with no pre-amp or anything ) input of the sound card and load the files from the DSP window (Load Settings icon). Make sure you have ver 3537 of the drivers and Max M's UFX pack! Comments and suggestions in this thread...
Here is the link:
http://www.angelfire.com/jazz/tigersplace/