LAN Party - Help!

Dear Toms network Guru's,

Some background:

My friends and I hold a private LAN party every few months. We play games 80% of the time but the other 20% is generally spent sharing files.

The venue is a friends house. He has a gigabit switch running to all rooms of the house, which is connected to a router for internet access and DHCP IP address assignment etc.

There are roughly 15 people present at the LAN on most occasions. Everyone is running Windows XP. Not everyone has gigabit ethernet cards in the computers, but many do.

The problem:
File sharing is an absolute nightmare. If one person is copying 1 file across the network, it is usually perfectly fine. if two people are doing it...again probably okay. As soon as 4 or more start sharing... everything drops to a crawl and we're lucky to get 1mb/s over the LAN. it fluctuates and 1 person is probably hogging 99% of the bandwith while everyone else stuggles.

We have 'allocated file sharing times' to avoid network clogging during gaming times, but generally this makes things worse because everyone tries to copy files at the same time.

The option is of course to 'baby' people and manage the people, not the network, but nobody at the LAN really wants 1 person going around policing everbodys usage. That would just ruin the atmosphere.

Help?:
There has to be some applications out there we can run to manage the traffic on the network. Can anyone suggest some good ones. I have played with applications like Netlimiter, but people find it annoying to have to adjust each time something changes. There has to be some more managable applications out there to assist us? Can anyone reconmend some names?

The network setup is pretty basic. We don't have any 'network specialists' among our group of friends. We all have basic knowledge, but clearly not enough to set up the network so it does not die as soon as more than 5 people try to copy a file simultaneously.

Our budget is not huge. We cannot afford to go out and spend hundreds of dollars on 'enterprise' type equipment, so we realise that this might be an uphill battle. I also ralise I might get responses such as "that's just the way it always is" but I'm hopeful for any help we can get that could possibly improve the network setup and performance for our LANs.

Thanks!

Tim