How to make a forum on my server?

Okay I have an old computer (running Windows XP Home) setting around that's always online via high speed internet (Cox Cable) and I've hosted a site on it, I'm not sure right now what I used or how I did it but I've got the site online. I want to make a forum for it but I am completely unsure how to do it. Any help would be appreciated. I'll go check on it in a second and give more info if needed. Sorry I'm not next to it right now and haven't touched it in months so it seems vague.

Also I've checked out phpBB and other things like it, I'm pretty computer literate but this is outside of my specialty.
Haha, I'm not illiterate, just woke up actually, I reread my post and it shows. Yeah I thought phpBB looked nice just didn't want to go about the tinkering without some direction or info first. I'm using Apache HTTP Server 2.2 and with just the defaults active. It's been awhile since I've played with any of this so I'm a bit out of practice. Thanks for the help.

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