That will work, but won't tell you where it exists, if that is important... If you need to know the install location, use a case statement, like this:
 Code:
; Assumes installLoc1, 2, & 3 are already defined...
Select
 Case Exist($InstallLoc1)
  $InstallLoc = $InstallLoc1
 Case Exist($InstallLoc2)
  $InstallLoc = $InstallLoc2
 Case Exist($InstallLoc3)
  $InstallLoc = $InstallLoc3
EndSelect
'Install location is ' $InstallLoc @CRLF
The numbered values determine the location and set the unnumbered InstallLoc variable, which is used for all remaining references to the location.

Since a Case statement stops after the first match, you can change the preference by changing the sequence of matches. If you need to make a decision based on the file existing in multiple locations, then more complex logic with individual If statements are required.

Glenn
_________________________
Actually I am a Rocket Scientist! \:D