XP, ICS and Apache

I have a two-computer home network, with Windows XP ICS sharing the connection.

PC1 Setup.
- Cable modem attached via Ethernet.
- ICS sharing CM connection.
- Norton Internet Security 2004 installed.
- IP: 192.168.0.1 internal, 81.108.39.29 external.

PC2 Setup.
- Connected to PC1 via crossover Ethernet.
- Can browse the Internet happily.
- No firewalls installed.
- Apache installed and monitoring port 80.
- IP: 192.168.0.2 internal.

So, the question is - how do I get requests to my external 81.108 IP to map across from PC1 to PC2?

I've tried most things I know, but now I'm pulling my hair out.

Any suggestions warmly welcomed!