Java Virtual Machine

What is my current version?

Microsoft Virtual Machine:
    (1) Start, Run. Type "wjview" and press enter. The top line shows the version. If you get an error, you don't have Microsoft's Virtual Machine.
Sun Java:
    Start>>Settings>>Control Panel.  Doube click the Sun Java icon, select about.

Where can I get VM?

Microsoft (Current version: 5.0.3810.0):
Update: Part of Windows Update
Install: No legal form of installation over the net, but Try Here or Here.
Sun Java (Current Version: 1.5.0):
Update And Install: Sun Java

I don't have Virtual Machine, why not?

Windows XP users may not have Microsoft Virtual Machine (VM) installed because it was believed that the users could do without this piece of software, but users still need VM for those websites with java applets such as Yahoo! Chat.  Windows XP no longer has Microsoft Java Virtual Machine through Service Packs.
All other users will have Virtual Machine.
See above for download locations.

Square, Circle and Triangle

This indicates a corrupted Virtual Machine installation, either Sun or Microsoft.
Whichever you use, use the above links to get a fresh version.

Disable - Enable Sun

Start, Settings, Control Panel. Click Internet Options.
Under the Advanced tab, find the "Java (Sun)" heading.
Check the Box underneath to Enable, Remove the check to disable. Close all Internet Explorer windows to make it have effect.
Microsoft will automatically disable/enable at the same time.

What is Java Virtual Machine

Those programs written in languages such as Pascal or C are compiled into executable files ready to be run.  They are OS dependant, IE one written for Windows wont run on Linux.  Languages such as Basic are interpreted each time they need to be executed on the users computer.  Java is different, first byte code is produced, then when its ready to be executed, they byte code is interpreted.  Java Virtual Machine is the software which interprets this byte code and runs a java program.  The java applets will not run without a virtual machine.  Java applets are not dependent on one OS, making it a very useful language to write it, as the same code may work over many different computers.

Sun Microsystems or Microsoft?

Supposedly they should be compatible, but please be aware Sun are the original producers of Virtual Machine.  They are however, not compatible due to Microsoft technologies being different.  Some applets are distributed in a way which only Microsoft Virtual Machine will run, therefore the Sun version does not work.
You can have both versions of Virtual Machine installed on your computer.  The control panel with the sun version lets you switch between it being default and not.  You can also set which one is used by these options in Internet Explorer:
Tools>>Internet Options, select advanced tab.  Scroll down to Java (Sun).  Placing a check by "Use Java 2...." will make Sun be the Virtual Machine to be used.

Sun v Microsoft

Due to a legal battle, Microsoft no longer distribute VM by Install On Demand (IOD).  Microsoft are granted the rights under their license to perform updates to, and distribute VM for a limited period, under certain agreements.  Sun seeks to make Microsoft issue VM as part of windows or internet explorer, and not as separate web downloads.  Sun also seek for their own plugin to be distributed with Windows and internet explorer.  Sun believe they are protecting users from outdated microsoft java technology.

Update: Extended License

Microsoft and Sun came to a joint decision to allow Microsoft to continue supporting and fixing security problems in Microsoft's VM until September 2004. This is to allow for developets to transition their Microsoft dependent Java code to the standard Java code. Sun will have agreed to this to protect Java - a sudden inability for people to run some java applets could destroy the platform.
If you use Sun Java (I recommend), and a applet wont run correctly, I suggest you get on to the service provider, they only have that 9 months to fix, before people really start having trouble - Microsoft VM redistribution is illegal.

Further Extensions

Microsoft and Sun came to further decisions to prolong the transition period. Microsoft may now support the Microsoft Java Virtual Machine software until December 31, 2007. This means security holes may be fixed as found, leaving a much more secure, longer transition time. As has been since 1997, no improvements or changes to the way the Java in the MSJVM works will be made, all that's ever changed in the last 7 years, and for the next 3 years is security holes.