Windows 7 with internal port redirection, is it possible?

Yes, windows does have a iptables equivalent, it is via the tool netsh and the portproxy interface.

The command to do what you want would be

netsh interface portproxy add v4tov4 listenaddress=YOUR_IP_HERE listenport=8080 connectaddress=YOUR_IP_HERE connectport=80 

Note, that this will only do IPv4 connections, if you also want to forward IPv6 connections you would also need to do

netsh interface portproxy add v6tov6 listenaddress=YOUR_IP_HERE listenport=8080 connectaddress=YOUR_IP_HERE connectport=80

AFAIK, Win7 has no iptables equivalent. Writing a server that does what you want (listens on a port, copies everything to/from another) should be easy enough. You can find one at this URL: http://www.quantumg.net/portforward.php (untested). Using a reverse proxy (Google is yout friend) may fit the bill for http-like traffic. Also check this post: https://stackoverflow.com/questions/3721000/port-forwarding-on-windows-7