To search the whole computer:
gdr -PSProvider 'FileSystem' | %{ ls -r $.root} 2>$null | where { $.name -eq "httpd.exe" }
I am pretty sure this is a much less efficient command, for MANY reasons, but the simplest is your piping everything to your where-object command, when you could still use -filter "httpd.exe" and save a ton of cycles.
Also, on a lot of computers the get-psdrive is gonna grab shared drives, and I am pretty sure you wanted that to get a complete search. Most shares can be IMMENSE with regard to the sheer number of files and folders, so at the very least I would sort my drives by size, and add a check after each search to exit the loop if we locate the file. That is if you are looking for a single instance, if not the only way to save yourself the IMMENSE time sink of searching a 10TB share or two, is to comment the command and highly suggest any user who were to need to use it should limit their search as much as they can. For instance our User Profile share is 10TB, at least the one I am on is, and I can limit my search to the directory $sharedrive\users\myname and search my 116GB directory rather than the 10TB one. Too many unknowns with shares for this type of script, which is already super inefficient with regard to resources and speed.
If I was seriously considering using something like this, I would add a call to a 3rd party package and leverage a DB.