The USB Guitar Link unit is by far the worst thing that I've ever purchased on Amazon.
First of all, it's a nightmare to install and configure, because it conflicts with your existing sound card.
When you make a change in the settings menu, you have to close the program, then reboot the computer to see what effect that had on its operation.
Most of the time, it failed to acknowledge that my guitar was even plugged-in.
When I finally got it to process my guitar, it sounded terrible. There was an enormous delay from when you hit a string and then hear the sound. You can alter the sampling frequency, but the delay is still ridiculously long - making the thing utterly useless.
I contacted the manufacturer - Native Instruments Gmbh (I think they're German) and they were no help whatsoever.
Avoid this thing like the plague.
My PC Spec: Pentium Dual Core 2.93 Ghz nVidia GeForce 9500 GTX Realtek HD Sound Card 3 GB of SDRAM Windows Vista Ultimate