Your problem is that your java is not installed correctly and doesn't show up on PATH environment variable. You need to add it manually.
To fix that problem, follow these steps:
Go to my computer and open C:\Program Files\
Find the java installation, as example my java is installed in C:\Program Files (x86)\Java\jre6\bin
Then you need to modify environment variables:
For Windows XP:
Start -> Control Panel -> System -> Advanced
Click on Environment Variables, under System Variables, find PATH, and click on it.
In the Edit windows, modify PATH by adding the location of the java to the value for PATH. Like "something;more;andmore;C:\Program Files (x86)\Java\jre6\bin". If you do not have the item PATH, you may select to add a new variable and add PATH as the name and the location of the java as the value.
Close the window.
For Windows Vista:
Right click “My Computer” icon
Choose “Properties” from context menu
Click “Advanced” tab (“Advanced system settings” link in Vista)
In the Edit windows, modify PATH by adding the location of the java to the value for PATH. Like "something;more;andmore;C:\Program Files (x86)\Java\jre6\bin" If you do not have the item PATH, you may select to add a new variable and add PATH as the name and the location of the java as the value.