For some reason I didn't include version numbers in Picture Slots 1 and 2.  I don't know why, I just didn't.  You can still get the version for earlier versions by finding the Picture Slots executable file, right click on it and select "Properties" then select the "Version" tab.
The Main Menu launch program has a "Version Check" option which will display the version of Picture Slots your are using.  The versions are represented by 4 numbers, for example 4.0.0.1 which equates to Major, Minor, Release, and Build.