One day, I tried to install Adobe Acrobat 8.0 but failed. I got error message” Windows installer service could not be accessed. This can occur if the Windows Installer is not correctly installed. Contact your support personnel for assistance.”. I also tried install ITunes but get the same error.
I changed Window installer service to active and automatic, and use command “msiexec /regserver”, still no go.
I heard another possible root cause is the presence of wow64 with data set as 1 under the key HKEY_LOCAL_MACHINE/SYSTEM/CurrentControlSet/services/msiserver, change value back to 0 may fix it. But still no go.
Finally, I used the below solution on my Win7, the issue fixed, hope it's helpful for you.
1. Start Regedit
2. Delete HKEY_LOCAL_MACHINE/SYSTEM/CurrentControlSet/services/msiserver
3. Restart computer
4. Copy this msiserver key from other (Vista or Win7)machine which works fine.
5. Re-install applications, issue resolved.