You write code. You write a program and specify where you can install it during the installation process. Doesn't it make sense to then have your installation program link all associated portions of this program you are installing (AND JUST SPECIFIED WHERE YOU ARE INSTALLING IT!) instead of making users go back after the fact and manually change a configuration file to link it.
It's funny how programmers don't see simple things like this as a failure of their codewriting abilities. They say, "Oh, yeah, just have them run regedit and modify this entry and change this and this." If you complain they tell you to just, "Be sure to have them back up the registry first."
I would like to see some of these programmers walk the average tech support call through a registry change on someone who knows NOTHING about Windows.
Note to programmers. Assuming you are writing code for people who are also programmers is stupid.