Please be careful with this! You need to add a path to your Windows Path Environment variable. You may wish to back up the current path in a file so you don't accidently erase something. I haven't done this on Vista. You may to find help online to this for Vista.

1. Make sure your logged in as the adminstrator
2. Start Menu > Control Panel
3. Double click on the "System" icon. If you don't see that, click on "Classic View" in the left column first
4. Select the "Advanced" tab.
5. Click the "Environment Variables" button.
6. Select PATH, and click "Edit"
7. At the end of the path, add the path to the "bin" file the Java JDK. In my system it was "C:\Program Files\Java\j2sdk1.5.0\bin" But yours may be different, so make sure to find it on your hard drive. Make sure this new location is separated by a semicolon from the other locations already in the PATH variable.
8. If you alread have a command window open, you'll need to reopen it.