Sorry, but what follows is copypasta:
This problem may occur if one of the following conditions is true:
* The Windows Installer files that are on your hard disk are damaged or are missing.
* You install or remove a program that uses the Windows Installer Microsoft Software Installation (MSI) package file (.msi). For example, this may occur when you try to install Microsoft Office on your computer.
Method 1: Reregister the Windows Installer
To reregister the Windows Installer, verify the location of the Msiexec.exe file on your hard disk and in the Windows Registry, and then reregister the Windows Installer. To do this, follow these steps.
Note Because there are several versions of Microsoft Windows, the following steps may be different on your computer. If they are, see your product documentation to complete these steps.
1. Determine the location of the Msiexec.exe file on your hard disk. To do this, follow these steps:
1. Click Start, click Run, type %windir%\system32, and then click OK.
Note This step will open the folder where the Msiexec.exe file is located.
2. Make a note of the location of the Msiexec.exe file. The location of the Msiexec.exe file will be a combination of the value in the Address text box and the Msiexec.exe file name itself.
For example if the Address text box contains a value of C:\Windows\system32, the location of the Msiexec.exe file will be C:\Windows\system32\Msiexec.exe.
2. Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:
322756 (http://support.microsoft.com/kb/322756/ ) How to back up and restore the registry in Windows
Make sure that the location of the Msiexec.exe file in Registry Editor is correct. To do this, follow these steps:
1. Click Start, click Run, type regedit in the Open text box, and then click OK.
2. Expand HKEY_LOCAL_MACHINE, expand SYSTEM, expand CurrentControlSet, expand Services, and then click MSIServer.
3. In the right pane, right-click ImagePath, and then click Modify.
4. In the Value data text box, type the location of the Msiexec.exe file that you determined in step 1, followed by the value of /V, and then click OK.
For example, if the location of the Msiexec.exe file is C:\Windows\system32\Msiexec.exe, type the following text in the Value data text box:
C:\WINDOWS\System32\msiexec.exe /V
5. Click OK to close the Edit String dialog box.
6. Click the File menu, and then click Exit to close Registry Editor.
3. Start your computer in safe mode, and then register the Msiexec.exe file. To do this, follow these steps:
1. Click Start, and then click Turn off computer or Shut Down.
2. Select the Restart option, and then click OK, or click Restart.
3. Press F8 before the Windows splash screen appears.
4. On the Windows Advanced Option menu, use the arrow keys to select the Safe Mode option, and then press ENTER.
5. If you use a dual-boot or multiple-boot computer, select the appropriate operating system from the list that is displayed, and then press ENTER.
6. Log on to the computer.
7. Click Start, click Run, type msiexec /regserver in the Open text box, and then click OK.
Note For 64-bit operating systems, you also have to reregister the 64-bit MSI installer. To do this, click Start, click Run, type %windir%\Syswow64\Msiexec /regserver in the Open text box, and then click OK.
On 64-bit editions of the Windows operating system, 32-bit binaries are located in %systemroot%\SysWow64 folder. The 64-bit binaries are located in the %systemroot%\System32 folder.
8. Click Start, and then click Turn off computer or Shut Down.
9. Select the Restart option, and then click OK, or click Restart.
If the issue persists, and you still receive the error message that is mentioned in the “Symptoms” section, follow the steps in Method 2.
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Method 2: Reinstall the Windows Installer
To reinstall the Windows Installer, rename the damaged Windows Installer files, and then reinstall the Windows Installer. To do this, follow these steps:
1. Click Start, click Run, type cmd in the Open text box, and then click OK.
2. Type cd %windir%\system32, and then press ENTER.
3. Type attrib -r -s -h dllcache, and then press ENTER.
4. Type ren msi.dll msi.old, and then press ENTER.
5. Type ren msiexec.exe msiexec.old, and then press ENTER.
6. Type ren msihnd.dll msihnd.old, and then press ENTER.
7. Type exit, and then press ENTER.
8. At the command prompt, type exit, and then press ENTER.
9. Click Start, and then click Turn off computer or Shut Down.
10. Select the Restart option, and then click OK, or click Restart.
11. Log on to the computer.
12. Download and install the latest version of the Windows Installer. For more information about how to obtain the Windows Installer, click the following article number to view the article in the Microsoft Knowledge Base:
893803 Windows Installer 3.1 v2 (3.1.4000.2435) is available
-http://www.microsoft.com/downloads/details.aspx?displaylang=de&FamilyID=889482fc-5f56–4a38-b838-de776fd4138c
13. Click Start, and then click Turn off computer or Shut Down.
14. Select the Restart option, and then click OK, or click Restart.
APPLIES TO
* Microsoft Windows Server 2003, Standard x64 Edition
* Microsoft Windows Server 2003, Enterprise x64 Edition
* Microsoft Windows Server 2003, Datacenter x64 Edition
* Microsoft Windows Server 2003, Enterprise Edition for Itanium-based Systems
* Microsoft Windows XP Home Edition
* Microsoft Windows XP Professional
* Microsoft Windows XP Professional x64 Edition