having a problem with windows xp + php

hi, I'm having a problem with windows xp using IIS 5.0 It's windows XP pro. I'm trying to run php as an ISAPI module (i may have screwed up the initals but i think thats it). Well everytime i follow the instructions in the php readme for use on IIS i have a problem. It will not load the dll. And PHP wont work. I've tried formating i've tried everything. Also It seems my IIS server has a user limit because when a couple poeople are on my site others get messages saying that the server can't handle anymore connections. Where in IIS can i specify the ammount of connections for it to handle (or can i even do that?) Is there some type of limit that IIS has for users? If anyone can help i would greatly apprecaite it. \ Thanks In Advance, Tyler