To update your PETROG4 software, please follow these steps.

These instructions assume you are running the native 64-bit version on a 64-bit system, and so refer to 
"Petrog4_x64.exe".  On a 32-bit system, or if you are running a 32-bit version on a 64-bit system, the executable 
name will be "Petrog4_x86.exe".

These instructions also assume that the install location for your existing Petrog4 executable
is C:\Program Files\Petrog4. Please substitute the appropriate path if it is different on 
your system.

1.  Go to C:\Program Files\Petrog4, and rename the existing Petrog4_x64.exe
to another name e.g. Petrog4_x64_ptxx.exe, where
xx represents the major part of the version number.

2. Copy the downloaded zip file to C:\Program Files\Petrog4, and extract the contents
to the current location ("Extract here"), saying "Yes" if prompted to overwrite existing files.  

3. Check that when you start PETROG from the desktop icon that the new version starts (on startup, the version number
and date are displayed).