Hi,
You can get by with a 1/4 to 1/8th adapter on your audio card, don't put into the mike inlet put into the an intlet with this mark ((())) AUX audio in. It will not get you a very loud sound but depending on what audio card you have, there should be a few options to get some reverb and other types of sounds.
My other suggestion is, get yourself a software called
Amplitube 2 (google does a nice job finding it
) which will give you a variety of options and is less expensive than Guitar Rig.
I am at work alright now, I have a link to some freeware and shareware softies I'll post later.
BossaMan