How to fix not being able to install programs

If you get the following error "The Windows install service could not be accessed." when trying to install programs you can follow these steps to correct the situation. These instructions are for Windows XP:

1. Be sure you're logged on with an administrative account.
2. Click Start Run.
3. In the Open box, type cmd. Click OK.
4. In the command window, at the prompt, type msiexec.exe /unregister and press ENTER.
5. Type msiexec /regserver and press ENTER. Next, you need to give the SYSTEM account full control permissions to the registry hive HKEY_CLASSES_ROOT. Back up the registry first. You can go here to find out how: Click Here
6. Open your registry editor and navigate to the following key: HKEY_CLASSES_ROOT
7. Click Edit Permissions
8. In the Group Or User Names list, check to see whether SYSTEM is listed. If not, click Add.
9. Ensure that the "From this location" box shows the local computer name.
10. Type system in the "Enter the object names to select" field, click "Check Names," then click OK.
11. In the "Group or User Names" list, click SYSTEM.
12. Check the Full Control check box under Allow.
13. Click Apply, then OK.
14. Close the registry editor and restart the computer.

If this doesn't work, you may need to do a repair of Windows XP (in-place reinstallation). Here are instructions on how to do that: Click Here