Mac-PC wireless networking. HELP! :-/

[soleole]

Hello!
I need some serious help here.
Ok, so this is my situation:

On one side: I have a PC which uses internet with a PC card (the ones with a sim card inside, with the service provided by T mobile, UMTS service) and the card also works as a wireless card.

On the other side: I have a new Macbook which I would LOVE to connect to the internet, sharing the PC's connection.
Clearly, is not possible to get a wireless router since the internet is provided via PC card, and is not a wireless network per se.

What I've done so far:
I've created a new P2P network, and now PC and Mac are wirelessly connected. However, I can't see the PC on the Mac or Mac on Pc nor share files, nor internet, clearly. I have enabled file sharing and internet sharing on the mac, and also on the PC.

I've done what they suggest in MacHelp and blah blah. I am completely new at this sort of thing so I really don't know what else to do, or it might be that I can't share this sort of internet, but even so, why can't I even share files? I'm sure is some sort of configuration somewhere...

Can anyone help?

Thank you!!!!!!!!!!!!!!!! :-)