Not too sure how you're going to run the game in a chat window - but I guess you are! So can't really advise on a php Chat class / application.
As for the forums - there are a number out there! phpBB, vBulletin, IPB etc...
If you want to setup your own website with these functions in there are some good CRM opensource solutions out there:
Look up:
i.e. Mambo, Xoops, phpNuke
All are well supported and provide login security and various functions (i.e. intergrated forums, chat applications etc.. ) to provide a feature rich website, quickly and generally easily 😉
Regarding your own localhost - most solutions will work on both Linux and windows - so no worries there, you will have to change config files when copying across to a live server anyway, so use whatever you have already or are most comfortable in.
There are apache / mysql / php packages available for easy install - check out LAMP, WAMP and easyPHP on google or get the components individually and install manually...