Create a System Restore Point and also make a Backup of Registry before Any mods on Registry. Do after Full data Archiving into CD-DVD-Tape-Cloud as the case may be. 

Start >> Run >> regedit  - opens the Registry editor

Another installation is ,,, in progress - When Add Hardware in Control Panel Clicked

This error can be encountered  for the Add Remove Programs in Control panel.

Keys Around Here -

HKEY_Local_Machine\Software\Microsoft\Windows\Installer\InProgress.
HKEY_LOCAL_MACHINE\System\Setup
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Factory

Types of Problem

FactoryPreInstallInProgress
Keys having 'Invalid Data'
Suspicious Entries

Remedy -

Change 1 to 0
Delete The Entry Itself

How to start the System Restore tool by using the safe mode option with the Command prompt in Windows XP

To start System Restore using the Command prompt, follow these steps:

1. Restart your computer, and then press and hold F8 during the initial startup to start your computer in safe mode with a Command prompt.
2. Use the arrow keys to select the Safe mode with a Command prompt option.
3. If you are prompted to select an operating system, use the arrow keys to select the appropriate operating system for your computer, and then press ENTER.
4. Log on as an administrator or with an account that has administrator credentials.
5. At the command prompt, type %systemroot%\system32\restore\rstrui.exe, and then press ENTER.
6. Follow the instructions that appear on the screen to restore your computer to a functional state.