Then make sure all the proper volume sliders are up in the windows mixer.
I use a Creative SB audigy card and choose the Creative ASIO driver in Guitar rig.
I send a line level signal into my SB sound card from my guitar pre amp and so I make sure the line in slider volume level is up about 90%.
You should see an input level meter move when you have the input into guitar rig set properly.
I have some info on my web site here about those setups.
http://www.el34world.com/Misc/Music/SoundPage1.htm
good luck.
I can give you my GR presets that I use if you get GR running.
I think you only get 30 minutes to try it though, which isn't much./