How to fully uninstall and reinstall ArcGIS

Origin,
In ArcGIS World, I saw a repost from rabbit babao, called "completely uninstall ArcGIS". Then I found the original ESRI Canada article, the original article is about how to completely uninstall and reinstall ArcGIS.

The focus of this article is to tell you that if your machine has installed ArcGIS in advance, it may not be clean to uninstall it only, in this case, you can use the setup with/cleanup on the ArcGIS desktop disc to clean up environment variables and registries. In this way, installing ArcGIS again is equivalent to installing ArcGIS in an environment where ArcGIS has not been installed before.

The post is as follows,
(Http://www.esricanada.com/english/suppo.../ilm15.asp)

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How do I do a clean uninstall and reinstall of ArcGIS?
How to fully uninstall and reinstall ArcGIS

Software: ArcGIS-ArcView, ArcEditor, ArcInfo
Software: ArcGIS (including ArcView, ArcEditor, and ArcInfo versions)
Version: 8.1.x, 8.2
Version: 8.1.x, 8.2 (suitable for version 8.3. note)
Platform: NT, Win 2000
Platform: NT, Win 2000

Cause: NA
Fault Cause: None

Answer:
Answer:
The following steps reset the environment variables and registry in order to do a clean installation of ArcGIS 8.1.x and 8.2.
The following steps initialize the environment variables and the Registry, and then install the brand new ArcGIS 8.1.x or 8.2.

1. Uninstall ArcGIS Desktop and Workstation versions (if applicable) by clicking Start> Settings> Control Panel. Double-click Add/Remove Programs.
1. Click Start> Settings> control panel, double-click Add/Remove programs, and uninstall ArcGIS desktop and Workstation versions (if any ).

2. Reboot your machine.
2. Restart your machine

3. Place ArcGIS Desktop CD in the CD-ROM drive.
3. Insert the ArcGIS desktop disc into the disc.

4. Cancel out of the Auto-Install window.
4. Cancel the pop-up automatic installation window.

5. Click Start> Run.
5. Click Start> RUN

6. Type this command: <cd-rom drive letter >:\ setup/cleanup
6. type the following command: <disc drive letter>: \ setup/cleanup

7. Make sure you type a space character after the word setup.
7. Make sure that you have a space character after the word setup

8. Click OK to start the process.
8. Click OK to start running.

9. Reboot and log back in as a user with administrative privileges.
9. Restart and log on to the machine as an administrator.

10. Remove and insert the CD again to start the autorun and install ArcGIS Desktop.
10. Pop Up and insert the disc again to start the disc to automatically run and install ArcGIS Desktop

11. Install ArcGIS Workstation (if applicable) by placing the Workstation CD into the CD-ROM drive.
11. If necessary, insert the ArcGIS Workstaion disc into the optical drive and install ArcGIS workstaion.

12. Don't do a cleanup with this CD.
12. You do not need to clear the ArcGIS workstation disc again.

13. Reboot and log back in as a user with administrative privileges.
13. Restart and log on to the machine as an administrator.