You can switch between the Sun Java™ Virtual Machine and the Microsoft VM. The Sun JVM can be enabled and disabled without having to uninstall it. Switching back and forth between these Virtual Machines can be done through the Advanced tab in your Windows Internet Options Control Panel, OR by using the Java™ Control Panel. Hint: it's good to check both places.
Instructions for switching between the Sun JVM and Microsoft VM using Internet Options:
Open Control Panel by clicking Start->Settings->Control Panel
Open the Internet Options window by double clicking Internet Options
Click the Advanced Tab
Find the "Java (Sun)" item and check or uncheck the checkbox which says
"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
Instructions for switching between the Sun JVM and Microsoft VM using the Java Control Panel:
Open the Windows Control Panel by clicking Start->Settings->Control Panel
Open the Java Control Panel by double clicking the icon labeled "Java Plug-in"
In the Java Control Panel, click the Browser Tab
Under the Browser Tab you will see checkboxes next to installed Web browsers.
Check or uncheck the checkbox next to the Web browser you want enable or disable from using the Sun JVM
Click the Apply button to save your settings
Restart Internet Explorer