The standard minijack aux-in is just no good. You need a manlier, guitar-ready audio input for your machine. Instructables’ shows you how, though commenter Steve Johnson points out that it won’t work well with the basic CD-in socket that some PCs are limited to.
Guitar/Mic In Port [Instructables]
I’d laugh at this if my PC didn’t have a cassette deck.
That’s cool and all, but it’s much more worthwhile to save up a couple hundred bucks and grab something with real preamps, like a Presonus AudioBox or similar.