The tips to switch easily between Sun Java Virtual Machine and Microsoft VM without installing is:
By just some changes in the setting you can enable and disable it.
This is possible by using Java Control Panel or Advance tab option available in Windows Control Panel.
Open Start > Settings > Control Panel > Internet Options
Select the Advanced Tab option.
Look for Java item and click on check or uncheck.
You will get the following message :
"Use Java 2 v 1.4.x for applet (requires restart)"
Check or uncheck the box next to Microsoft VM
Save your changes by clicking the OK button
Restart the browser
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