How do I change my windows 9 back to factory windows 7?

I updated my Windows 7 to windows 9 and now computer runs slowly and it always shows window saying there is error. I want to go back to factory settings. How do I do this?

Are you asking about Windows or Internet Explorer?

Here's a place to start:
http://windows.microsoft.com/en-US/windows7/help

Be sure to back up all your user files before you wipe 9 and reinstall 7.

There's also a Windows 7 forum where you can ask specific questions if you get stuck along the way:
http://windows7forums.com/windows-7-support/