Unfortunately, there's no shortcut for the tool in the Start Menu, meaning you'll have to open Registry Editor it by executing it from a command line. Don't worry, it's not at all hard to do.
Follow these easy steps to open Registry Editor:
Note: You can open Registry Editor this way in any version of Windows that utilizes the registry, including Windows 7, Windows Vista, and Windows XP.
Click on Start.
In Windows XP, click on the Start button and then click Run....
In the search box, or Run window, type the following:
and then press Enter.
Note: Depending on your version of Windows, and how it's configured, you may see a User Account Control dialog box where you'll need to confirm that you want to open Registry Editor.
Registry Editor will open.
If you've used Registry Editor before, it'll open up to the same location you were working in last time. If that happens, and you don't want to work with the keys or values at that location, just continue to minimize the registry keys until you've reached the top level, listing the various registry hives.
You can now make whatever changes you need to make in to the registry.
Important: Considering the impact that the registry has on your computer, I highly recommend that, before you get started, you either backup the entire registry, or backup the individual registry keys that you're planning on working with, whatever is more appropriate for what you're planning on doing in Registry Editor.