Windows xp is marvelous in this aspect...
Heres your setup...
Nic A Wireless connection PC1
Nic B Wired connection PC1
Nic C Wired Connection PC2
Connect Nic B to Nic C with a crossover cable
Configure Nic B as 192.168.100.1 with a subnet of 255.255.255.0
Configure Nic C as 192.168.100.2 with a subnet of 255.255.255.0
Configure Nic C with a gateway of 192.168.100.1
Configure Nic C with DNS server information from Router
On PC1 highlight Nic A and Nic B right click either nic and choose bridge connection from the menu...
Thats quick and dirty xp routing...
Or...
http://www.practicallynetworked.com/sharing/xp_ics/
and do ICS
Tek