Newbie Need HELP - Computer Music Hardware

[pixelcrafter]

Dear Friendz ...

I am pixel. I've got technical problem here.
Please help me.

I used to make music with my laptop and everything works.
Since my laptop's RAM is limited,
I have bought used PC as it sold in a great price.

The problem is :

I want to use this PC to record my guitar
and make a nice song in the Cubase SX3.
I connect my guitar to the mic line in of the soundcard (creative sblive 7.1).
Then i use Guitar rig2 as the plugin of Cubase SX3.

semi acoustic guitar --> mic in soundcard --> guitar rig2 --> Cubase SX3

unfortunately, the guitar effect in the guitar rig2 is fail to produce the sound.
The only sound i hear is the original nylon sound of my semi acoustic guitar.

Is there anything wrong?
How can i possibly turn on the effect of the guitar rig2,
so i can hear the nice electric guitar sound.

This is my hardware&software specs:
Mainboard = GIGABYTE GA-M61SME-S2
Processor = AMD 64 Athlon X2
RAM = 3 GB
HD = 250 GB
S.CARD= Creative SB live 7.1

Thank you for your help.

-Pixel-