TechTips for When Windows Installer Service Cannot Be Accessed in Vista

If you have seen the error "The Windows Installer Service could not be accessed. This can occur if you are running Windows in safe mode, or if the Windows Installer is not correctly installed. Contact your support personnel for assistance", then you probably have spent a lot of time trying to find a solution. Well there are many things you can try to fix this and many of them will work for one machine but not another. The only fix I found that worked for me is a registry fix. The only problem with the fix I am going to suggest and explain is that it doesn't always work with Windows Vista and you need a good working copy of Vista to get the registry key you need in order to fix your problem. I wish I could say definitively yes this will work every time but I can't. I will also provide you with some links to Microsoft pages with suggested fixes that some people report working, but I didn't have success with them.

So first what causes this? It's most likely that your windows installer has become corrupted, which if it doesn't work you won't be able to install/uninstall any programs. Hence the error you are getting about the installer service not being accessed. The fix I suggest is the following.

The Fix that worked for me - Registry Fix

This one is a pain because you need another computer running Vista that has the installer service working. Not everyone will have two Vista PC's at their disposal, but this does fix the issue most often. You will want to do the following.

1. Open the registry on the working Vista machine (Click Start>>Run>>type regedit)

2. Navigate to the following key HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\msiserver

3. Right click on the key name and choose EXPORT

4. Save it to a USB flash drive, if you don't have one burn to CD\DVD

5. Now open the registry on the broken Vista machine and open the registry (Click Start>>Run>>type regedit)

6. Click File>>Import>>Locate the exported registry key>>Click Open

7. Once the key is imported it will give you a message saying it has completed

8. Reboot and test and see if you can install your program

9. If it worked you are done, if not then go to #2

This fixed my PC without any problems, the registry key imported just fine and after a reboot I was installing programs again. If you don't have a second copy of Vista to get the registry key then I can provide you with the key that I used. I have uploaded it here (a free file hosting site).

Now if that doesn't work for you I won't say you have to reinstall yet. I would suggest trying the information in the following link. It's a Microsoft page that explains how to fix this problem in XP. I have heard that it works in Vista and XP but I tried it on my 64-bit Vista and it didn't work for me. The only fix that worked for me was the registry key.

Also some people have reported that installing the Windows Installer 4.5 will fix the problem before it installs the needed software. Again I didn't have any luck with it but if neither of the above fixes worked it might be worth the 15 minutes it will take to download and install the installer just to see. Otherwise I suggest either restoring your PC to one of your restore points (if you have that setup) or reinstall Vista. Not good alternatives but they will cure your problem.