how to see what's installed and where?

[sandwichs]

ok... I don't really know how to install sofware under linux so.. I followed a tutorial that seems cool... (just in case here is the address) http://www.devshed.com/Server_Side/PHP/SoothinglySeamless/page1.html
the problem is that the sofware version they use are not the same as the one I could download.
Another problem is that I don't know how to see what I have installed on my machine. for example, I typed locate apache....well...I got some apache files in many directories BUT if I click Apache config (in KDE Kontrol Panel)... it says, install the package.. So, is it installed or not? I'm confuuuuuuuuuuuuuuse

[kannabis]

One command that might help you out a bit is "whereis filename". If you're using redhat, then it's pretty easy to keep track of those files. Assuming that you installed an rpm package, then the command would be rpm -ql package.name.rpm

that will show you where ALL the files in that package got dumped to.