You will see much more consistent returns in a pool; low or medium end hardware will take months to generate blocks nowadays.
If you do decide to mine solo, you need to have Bitcoin running as a server. There are two ways to do this - 1, start bitcoind.exe
(found in a subfolder) or pass an argument to bitcoin: bitcoin.exe -server
Once you do this, you have to set up a username and password in a config file somewhere. Check mining forum and/or www.bitcoin.it/wiki/Mining
for details. You will give this information to your miner, along with the IP to connect to (probably localhost or 127.0.0.1). RPC = 'remote procedure call', i.e. the miner is trying to talk to a server.