Secret Agent

Can someone explain the proper way to enable php suexec support on a cpanel box? Reason I ask is because I tried it a few months back, and what happened was it causes all sites immediately popup a "save file as" dialog instead of properly displaying the websites.

I am using apache 1.33, php 4.4.2

What would cause that to happen and how would I go about fixing it?

Also, what would the customers have to do to should they face any conflicts? I remember a 500 error issue mentioned on cpanel forums