X advice and housekeeping

SuSE 7.0, Kernel 2.2.19, XFree 4.1 Being relatively new to Linux, I never know what happens to older files when installing newer versions. For example, after installing (successfully, thank God) XFree 4, are there any disadvantages to removing the older version and what can be removed? X and SAX2 was installed with the RPM's from SuSE. Eric