[rondebmar]

I had IE9 on my laptop (Windows 7) but I didn't use it (I use Google Chrome) and deleted it using Add/Remove Programs.

Recently I wanted to install it, so I downloaded the installation file, but when trying to install it, I got the message that installation won't complete because it is already on the computer. It is not listed in the programs, and a search comes up with only the installation file which I had just downloaded. What is going on?

[DaveA]

Go to Control Panel, then Programs and Features.
Then on the left side of the pane, select "Turn Windows Features on or off".
Let it load as it may be VERY slow.

Then make sure that IE 9 is checked and then OK yourself out.

[DoubleHelix]

You can't uninstall Internet Explorer. You must have rolled it back to version 8. Rolling back IE is risky, and it looks like it bit you.

Post the exact and complete error message. You may need to repair Windows or reinstall the service pack.

[davehc]

You can uninstall IE9 through the Control panel - Programs and features - "View installed updates". Scroll down, almost to the bottom, and right click the IE9 update - uninstall. But, doing this, leaves only IE 8 in the path suggested by DaveA. But, It is not stated how rondebmar uninstalled IE9. If he did not follow the path I have outlined, I would suggest, first, that he does so to make sure it is properly uninstalled. And/or - go to windows updates and check for new updates. It will come up with IE9. Accept it and you may be back in business. But, as Doublehelix points out, you can runn into difficulties, and my suggestion may leave you with IE8 on the desktop. But it has worked several times for me.