Bincoin, mIRC, and Firefox over Tor
Get a copy of Tor
The fastest way to use Tor on Windows is to get one of the Bundles. All are available at  The Browser Bundle contains a copy of Firefox already configured to use Tor. The .exe's are self-extracting archives. You can install wherever you want.
Configuring Bitcoin is straightforward. Open the Settings menu and click Options. Check the box labeled Connect though socks4 proxy. The default proxy IP and port are the correct settings for using Tor.
In mIRC, go to Tools > Options > Firewall Change firewall support to "both," and the protocol to Socks5. Change the Hostname to 127.0.0.1 or "localhost" and change the port to 9050.
In the Tor Browser folder that you installed Tor in earlier, there should be a file called Start Tor Browser.exe Run it. The Vidalia Control Panel will open, displaying the status of the Tor connection. It will connect to Tor. When it's done, it will launch its copy of Firefox Important: If you exit the copy of Firefox that it launches, Vidalia will automatically shut down.
Restart Bitcoin and mIRC
To ensure that these programs are actually connecting via Tor, close and reopen them.
Guide to using tor with freenode: http://blog.freenode.net/2010/01/connecting-to-freenode-using-tor-sasl/