Wireless Internet

i have a Linksys wireless-G router (model WRT54G) i have it hooked up to my PC that runs on Windows XP. Upstairs i have a Mac Mini, i bought a Linksys Wireless-G USB 2.0 Network Adapter with SpeedBooster (model WUSB54GSC)
i was told by the technology chairman at school that it would work, by linksys, and by best buy. I feel like i have done everything i could to figure this out and i need help, big time. If someone could do a step by step, or just tell me what i need to do that would be great. thank you.

Maybe this advice would help:

WUSB54GSC Installing problems - Wireless Adapters - Linksys Community Forums