Home machine. There is is an online game where groups of people have fights\tournaments. Some teams are DDosing each other... Only thing I could read on helping against it was to contact your ISP to get them filtered out.. But doesn't sound very effective to me with Dynamic IP's
Not much you can do in a home machine even if your ISP is willing to help you.... a small DDoS can bring down your machine. Online games are full of kids with access to Zombies... or they just use LOIC...
Hmm really good question.. All I can think right now is set aside extra network bandwidth and server processing capacity to withstand sudden surges in traffic
Or you could try to find and start using a more (secure) online game, where the players are more (serious about gaming) and focusing on the game instead of sending DDOS attacks! That's just silly BTW, what Game are you talking about?
You might like to give a try to this one firewall (always rock solid on XP, even if development is at a halt for now)... http://www.ccsoftware.ca/8signs/synflood.cfm (does not work on x64, so I did not try it on win 7)
If that is the way they are getting your IPs chances are they using LOIC or a similar weapon... meet in a different place than IRC..
You can use cloak for IRC (hide your hostname with IP address - doesn't work if you are logged from webchat or webclient) also use SSL connection in your IRC client.
If your IRC server does support some sort of IP spoofing/vhosting (like on Undernet, if you logon to your username, it's possible to hide your real IP), contact the IRCops or any channel service personnel and ask for assistance. Other than that, you may want to purchase a Shell, with a couple of extra background processes, install psyBNC or other IP bouncing software such that your real IP is hidden from plain view Hope this helps!