Network/IP under DDoS attack

Hello everyone :o

a while back my oldest son got in a conflict with players through an online game. Ever since, our internet has been horribly laggy or disconnecting during regular hours. It's almost impossible to use the internet. Initially I called our ISP and ask what was going on. They told me that somehow, they (the other players) managed to get their hands on my son's IP-address (and thus mine). They've been targetting our Network/IP with so called icmp/igmp files, also called ''DDoS attacking''. The ISP said they could see this because our security-log had a bunch of SYN flood warnings (I have no clue for the rest what these are). I've followed an online tutorial on the internet how to block these files through Firewall. However, it seems a lot of these files are still slipping through my Firewall.

I wonder what else I can do. My ISP told me to wait it out, but it has been going on for over a week now and I really want this resolved.

Extra information:
We are all using Windows 7 Home Edition.

Thanks in advance and I hope to hear from someone soon,

Desperate mom