Searching files in folders defined in PATH

And easy way to do this is using the "where" command:

C:\>where reg.exe
C:\windows\system32\reg.exe

Refernce:

WHERE [/R dir] [/Q] [/F] [/T] pattern...

Description:
    Displays the location of files that match the search pattern.
    By default, the search is done along the current directory and
    in the paths specified by the PATH environment variable.

See example:

(Thanks to Cameron Skinner for this tip.)