Here is some example code.

Code:
Break On
Dim $SO
$SO=SetOption('Explicit','On')
$SO=SetOption('NoVarsInStrings','On')
$SO=SetOption('WrapAtEOL','On')
 
; Dim the variables
Dim $Key, $ReaderVer
; Set the $Key var to the key we want to read
$Key = 'HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\App Paths\AcroRd32.exe'
; Get the file version from a registry read into the $ReaderVer variable
$ReaderVer = GetFileVersion(ReadValue($Key,''),FileVersion)
; Do an If Else EndIf check on the version to decide what to do
If $ReaderVer < "6.0.3.2004113000"
  ? 'Adobe Reader is too old: ' + $ReaderVer
  ; Run code to update the reader
Else
  ? 'Adobe Reader is up to date: ' + $ReaderVer
  ; No update required.  Continue with rest of script
EndIf