When running p2pool at the same time as Bitcoin and Litecoin, I experienced that one port clashed between each other.
However this was a very easy fix.
P2Pool for Bitcoin: run_p2pool.py username password --p2pool-port 9335
P2Pool for Litecoin: run_p2pool.py --net litecoin username password
For litecoin, you need to go into %AppData%/Litecoin and create litecoin.conf with:
rpcuser=<pick a username>
rpcpassword=<pick a password>
server=1
and you're ready to go !
