Close...Maybe something like this is what you're after?

 Code:
Dim $Arrayoflocations, $foundLocation
$Arrayoflocations = "%programfiles(x86)%\putty", "%userprofile%\tools\putty"

For Each $location in $Arrayoflocations
   If Exist($location)
      $foundLocation = $location
   Endif
Next

If Len($foundLocation)
   ; Do Stuff Here If Installation Found
   "Install Directory Found: "+$foundLocation ?
Endif