Installing the "action pack"?

Click Start, click Settings, click Control Panel, double-click System, and then click the Environment tab. In Windows 2000, click Settings, click Control Panel, double-click System, click the Advanced tab, and then click Environment Variables.

Looking at this part in the first MS link doesn't look too difficult to check does it?

Open an extra browser window, walk through the points mentioned without doing anything you're unfamiliar with, only look what there is.

In the Regedit i make it a habit to look at he key mentioned and only touch the + and - before the folders and looking without ever making any changes i am not completey convinced of. Don't change any values if not really told to do so.

Only looking and opening and closing folders in the left panel doesn't immediately damage your registry.
It's time to learn to know your system little by little and knowing what you do, write it down, what , where so you might be able to put changes back ifnecessary. You're on XP so you can get back to a former restore point anyway.