How to Check for a Java Version
Sun Microsystems releases new versions of Java Runtime Environment, its essential Web plug-in, on a regular basis. Keeping your version up-to-date is necessary if you want to enjoy the latest rich Web content, but with so many versions, you may have a hard time keeping track of the one installed in your browser. Fortunately, the answer is right there on the computer, waiting to be discovered.
Click the Start button, and select Run from the Start menu.
Enter "cmd" (without the quotation marks) in the Run field, and then click the Run button.
Enter "java -version" (without the quotation marks) at the command prompt and press Enter.
Look at the text that appeared below the command prompt. It includes the currently installed version number and information.