dual web servers?

Hi, First of all. NEWBIE ALERT!...... For all those still here, I have a question. I currently have an NT server using Domino R5 as the web server. It is our production machine. I want to gradually get rid of it and use php and IIS (Apache later but have to use IIS to start.) Can I have both web servers running on the same machine? at the same time? For instance if I use the php 4.05 windows installer it will automatically configure IIS so how does that affect Domino web server and the current state of the website. I need to do some php testing before I can ditch Domino but don't want to mess up what I already have. I hope this makes sense. Any suggestions Thanks so much, Deb