If you have a standard Windows system, your Java will automatically look for updates and offer to install them.

Oracle have now set things so that if you have Java 7, it will automatically update this to Java 8.

This will cause your system to fail because Tomcat will not be able to find Java - because it will be looking for Java 7 which is no longer there.

If you have not yet encountered this problem, you should use Control Panel|Java to turn off Java's automatic update feature.

If you do encounter this problem (ie you say Yes to a Java update) and then OpenVPMS cannot be started, then you can fix the problem by uninstalling Java 8 (using Control Panel|Programs and Features) and then install Java 7 after manually downloading Java 7 from

 https://www.java.com/en/download/manual_java7.jsp

If you are reading this after April 2015, the above link may not work (because Oracle is removing Java 7 from easy availability in April 2015) and you should use

http://www.oracle.com/technetwork/java/javase/downloads/java-archive-downloads-javase7-521261.html

You may find the following useful (it is the sequence I used to examine and fix this problem on one user's system):

Diagnostic procedure:

1. Use Control Panel|Administrative Tools|Services to see if Apache Tomcat was running.  Was not.
2. Used Windows Explorer (ie Start|Computer ) to call up C:\Program Files (x86)\Apache Software Foundation\Tomcat 6.0\logs and delete all of them. [There will be a large number of files there, and it is easier to start with a clean slate.]
3. Start Apache Tomcat using Control Panel|Administrative Tools|Services
4. Look in logs to see if there is anything useful – I could see error messages but they did not say anything useful to me
5. Use Windows Explorer to find C:\Program Files (x86)\Apache Software Foundation\Tomcat 6.0\bin – in there is a file Tomcat6w.exe – double click to start it.
6. Look at the Java tab – this says where it expects the Java Virtual Machine to be – in your case it said something like C:\Program Files (x86)\Java\jre7\bin\client\jvm.dll
7. Use Windows Explorer to check that this is present – AHAH – have Java 8 – ie the above is not there but C:\Program Files (x86)\Java\jre8\bin\client\jvm.dll is there
8. So two problems: a) Java 8 installed but is not supported for OpenVPMS; b) Tomcat is looking in the wrong place
9. Fix = a) uninstall Java 8; b) install Java 7

Regards, Tim G