Q:

How to find where Apache's httpd.exe is installed?

How do I best figure out if and where Apache is installed on a windows machine?
I'm writing a script that uses the installed apache, but sets up it's own config & server-root, and I don't want to hardcode it nor have the user explicitly set it (unless necessary).
I tried to search the registry, but couldn't find anything useful.
Update for those posting default paths
On my machine, it was in C:/Program Files/Apache Software Foundation/Apache2.2. And if I had Vista 64-bit, it'd probably be under 'Program Files (x86)'. And if the computer doesn't have an English OS, it's even worse.
Workaround
Guess I have to check %PROGRAMFILES% for Apache 2.0 or 2.2's default path, then fall back to a prompt. It's be nice to read the registry and find out exactly where it is. 
Final note
Apache was not installed for 'Everyone', but only the current user. That makes it a bit more difficult to find as there are no services nor registry keys/folders to point there.

A:

I apparently installed Apache only for me (current user), not for all users on my machine, hence no registry key. 
If installed for all users, the registry key is here:
HKEY_LOCAL_MACHINE\SOFTWARE\Apache Software Foundation\Apache\2.2.xx\ServerRoot

