Unless WAMP auto starts Apache and/or MySQL (when Windows loads up), you shouldn't have any problems having both WAMP and XAMPP installed. You will have problems if you try to run them at the same time, which is why you should check that WAMP isn't running, which would explain why XAMPP can't then run.
And as far as why things have to be so complicated; Taking something complicated and making it easy, isn't easy!
Are you just looking to try out Tiki? You could try using a LiveCD first, so you can get a feel for what Tiki is like, without having to install anything (Everything runs from the CD without modifying your computer)