First of all Welcome to TDF forum jack.
I am not sure whether this will work with Data card or not , but this works like charm with My Ethernet based Broadband.
You need to understand ICS(Interent connection sharing) for this.
You need to connect your PC to laptop either using a Wifi-Wifi based connection or ELAn-ELan based connection.
Goto Control Panel->Network and connections.
Change adapter settings. ( Here you have to enable your wi-fi/Ethernet adapter device in the laptop).
Now goto Data card connection properties and you will see a tab called "sharing".
Click on the tab , and you will get a option to place a check mark. It will say "Allow other computer to connect to internet using this computer's internet connection.? ".
Place a check mark over there , and in case if it asks you for choosing which adapter you will like to use then select "Wifi/Ethernet device".
It will enable DHCP server on your laptop and will assign an I.P. address to device connecting to it.
Now create a New Ad-Hoc networking profile on your laptop (for wifi based connections).
Once you have created an Ad-Hoc wi-fi network on your lappy , open your PC and connect to the laptop using the wi-fi/Etherent.
Now select the "Home Network " option over there, once the IP has been assigned.
Notes : Make sure theLAN/Wi-fi Adapter present on your PC has "Automatic IP assignment enabled." else it would become a PITA for ICS and may not work.