Try using the Windows Installer CleanUp Utility. As long as you installed the application using the Windows Installer, this utility will remove all the folders, files, registry keys, and entries from your system and allow you to start over with a clean slate.
Download the Windows Installer CleanUp Utility
Locate and run msicuu2.exe to install the Windows Installer CleanUp Utility.
Locate and launch the Windows Installer CleanUp Utility on the Start menu.
From the Windows Installer CleanUp Utility window, locate the application in the list and click the Remove button.
Once the application has been removed, click the Exit button to close the utility.
You also need to address your issue that your Add/Remove Programs tool won't open.
Run the System File Checker
Go to the Run box on the Start Menu and type in:
sfc /scannow ( sfc if not reconized) (Note that there is a space between sfc and /scannow)
This command will immediately initiate the Windows File Protection service to scan all protected files and verify their integrity, replacing any files with which it finds a problem.
In all likelihood you will be prompted to insert the Windows XP CD.