Unable to open win installer package

If you are sure about your package, it can only be your Windows Installer.
Reinstall it by following these steps:

1. Log on to the computer as an Administrator.
2. Stop the Windows Installer service. To do this, proceed as follows:

1. Click Start, then Control Panel.
2. Click Switch to Classic View (if you are not already using this display mode).
3. Double-click Administrative Tools, then double-click Services.
4. In the list of services, right-click Windows Installer, then click Stop from the context menu.
5. In the File menu, click Exit.
6. Close the Administrative Tools window.
3. Click Start, then Run.
4. In the Open box, type cmd, then click OK.
5. Navigate to the \Windows\System32 folder. So please type: "cd\windows\system32", then press ENTER.
6. Rename the following files:

Msi.dll
Msiexec.exe
Msihnd.dll

You can rename these files using the ren command.

Examples: type "ren msi.dll msi.old" then "ren msiexec.exe msiexec.old" then "ren msihnd.dll msihnd.old"

The Msi files are then renamed to Msi.old

7. Once all files are renamed, type exit, then press ENTER.
8. Insert the Microsoft Office XP CD.
9. Click Start, then My Computer.
10. Under Devices with Removable Storage, right-click the CD-ROM drive containing the Microsoft Office XP CD, then click Open from the context menu.
11. Double-click INSTMSIW.EXE (software to install "Windows Installer" inside Office) at the root of the Microsoft Office XP CD-ROM.
12. Click OK in response to the message confirming the successful installation.
13. Restart your computer.