Eclipse - no Java (JRE) / (JDK) ... no virtual machine

Eclipse will by default try to launch with the default "java.exe" (the first one referenced by your PATH)

Three things to remember:

• "Installing" a JRE or a JDK can be as simple as unzipping or copying it from another computer: there is no special installation steps, and you can have as many different JVM versions (1.4, 5.0, 6.0...) as you want, "installed" (copied) almost anywhere on your disk.
• I would recommend to always run Eclipse with the lastest JRE possible (to benefit from the latest hotspot evolutions). You can:
  • Reference that exact JRE path in your eclipse.ini.
  • Copy any JRE of your in your <eclipse>/jre directory. In both cases, no PATH to update.
• The JVM you will reference within your Eclipse session is not always the one used for launching Eclipse because:
  • You only need a JRE to launch Eclipse, but once Eclipse launched, you should register a JDK for your projects (especially for Java sources and debugging purposes, also in theory for compilation but Eclipse has its own Java compiler) Note: You could register just a JRE within Eclipse because it is enough to run your program, but again a JDK will allow for more operations.
  • Even though the default registered Java in Eclipse is the one used to launch the session, you can want to register an older SDK (including a non-Sun one) in order to run/debug your programs with a JRE similar to the one which will actually be used in production.

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June 2012, jmbertucci comments:

I'm running Windows 7 64-bit and I had the 32-bit JRE installed. I downloaded Eclipse 64-bit which looks for a 64-bit JRE. Because I didn't have the 64-bit JRE it threw the error, which makes sense.

I went to the Java manual install page (which was not as directly accessible as you'd like) and installed the 64-bit version. See "Java Downloads for All Operating Systems". That was all I needed.

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April 2016: Steve Mayne adds in the comments:

I had to edit the eclipse.ini file to reference the correct Java path - Eclipse doesn't use the environment PATH at all when there is a value in eclipse.ini.

Just copy this file :

c:/Program Files/Java/jre(5,6,7..any version)/bin/javaw.exe

to Eclipse Folder

*note only tested for Windows

All the other answers about setting only the JAVA_HOME are not entirely right. Eclipse does namely not consult the JAVA_HOME. Look closer at the error message:

...in your current PATH

It literally said PATH, not JAVA_HOME.

Rightclick My Computer and choose Properties (or press Winkey+Pause), go to the tab Advanced, click the button Environment Variables, in the System Variables list at the bottom select Path (no, not Classpath), click Edit and add ;c:\path\to\jdk\bin to the end of the value.

Alternatively and if not present, you can also add JAVA_HOME environment variable and make use of it in the PATH. In the same dialogue click New and add JAVA_HOME with the value of c:\path\to\jdk. Then you can add ;%JAVA_HOME%\bin to end of the value of the Path setting.