A big chat network : Help me to realise my dream

[DomainEmpire.com]

More than 2 years ago, we launched a free chat community using free softwares on www.chatowner.com with excellent results and more than 6k visitors in few weeks of work.

Live chats and thousands of happy visitors.
For some reasons, some of these companies which were offering such softwares, closed their activity and we left the project for a while.

Today www.chatowner.com have only few remaining chats but still over 1,000 daily visitors.

I'd like to realise my dream with a powerful Irc chat software (multiple features, able to keep over 10k of simultaneous connections) and a leased server (or, maybe, one of my property).

Now, all this is surely expensive in terms of bandwidth and I could have many attachs by "little hackers" as always happens in this kind of communities.

In few words, what would be the first step to launch this project ?
Where could I get the BEST software today on the market with the best features to realise my chat network ?
Considering I've really no experience with a server, what should I do exactly to put one in service ?

Ok, still better.
Suppose I buy a Pc with 100Gb hard disk (the best machine on the common market without going too expensive), supposing I can already get a static Ip by a local provider and I can talk with them about bandwidth, what next ?

In bried: what installing to transformate this machine in a server ?
Really no idea ...
What doing to have my own dns etc ... ?
Thanks all, this's really important for me.

How protecting our network by external attacks ?
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For "Chat Network", I mean a big network with dozens of topic channels, an Irc Server so anyone can connect using a common Mirc program and the possibility to give other webmasters an html tag to put a free chat on their sites too.

Thanks again, any suggestions would be highly appreciated.




P.S.: The best thing would be purchasing full copyrights on a full software but this would be too expensive, I'm afraid ... consider the first year we'd have SURELY no sponsor :(