Ok, You dont need to use two cables.
Use your cross over cable to connect to each PC. Then which ever PC has the Internet Connection you are going to share run the steps below.
Through Internet Connection Sharing for network and dial-up connections, you can use Microsoft Windows XP to connect your home network or your small-office network to the Internet. For example, you may have a home network where a Windows XP-based computer can connect to the Internet by using a dial-up connection. If you enable Internet Connection Sharing on the computer that uses the dial-up connection, you can provide network address translation, addressing, and name resolution services for all the computers on your network.
Note that to enable Internet Connection Sharing, the Windows XP-based computer must have two network adapters, one for the home network or the small-office network, and one for the Internet connection. Setup procedures
To enable Internet Connection Sharing on a network connection, follow theses steps: 1. Click Start, click Control Panel, and then double-click Network Connections.
2. Click the local area network (LAN) connection or click the dial-up networking connection that you want to share (that is, the one that connects to the Internet), and then under Network Tasks, click Change settings of this connection.
3. On the Advanced tab, click to select the Allow other network users to connect through this computer's Internet connection check box.
4. If this is a dial-up networking connection, and you want the connection to be automatically dialed when another computer on your network tries to connect to the Internet, click to select the Establish a dial-up connection whenever a computer on my network attempts to access the Internet check box.
5. If you want to permit other network users to enable or to disable the shared Internet connection, click to select the Allow other network users to control or disable the shared Internet connection check box.
6. Under Internet Connection Sharing in Home networking connection, select the connection that connects the computer that is sharing its Internet connection to the other computers on your network.
Note that to enable Internet Connection Sharing in Windows XP, you must have administrative rights.
Important When you enable Internet Connection Sharing, the network adapter that is connected to the home network or to the small-office network receives a new static IP address of 192.168.0.1, with a subnet mask of 255.255.255.0. Existing TCP/IP connections on the network may be lost and must be reestablished.
Configuration and usage issues
Internet Connection Sharing is intended for use in a small office or in a home office where the network configuration and the Internet connection are managed by the Windows XP-based computer where the shared connection resides. It is assumed that on this network, this computer is the only Internet connection, this computer is the only gateway to the Internet, and this computer sets up all internal network addresses. All hosts on the network except the Internet Connection Sharing host are expected to be configured to obtain an IP address and DNS configuration automatically.
You cannot modify the default network configuration after you enable Internet Connection Sharing. This includes changing the range of private IP addresses that are handed out (DHCP allocator), enabling DNS, disabling DNS, and configuring a range of public IP addresses.
If your home office users have to gain access to a corporate network that is connected to the Internet by a tunnel server, the users must create a virtual private network (VPN) connection to tunnel from the computer on the Internet Connection Sharing network to the corporate tunnel server on the Internet. The VPN connection is authenticated and secure. Creating the tunneled connection allocates correct IP addresses, DNS server addresses, and WINS server addresses for the corporate network.