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#71
This is what and how you need to reinstall Windows, just like we suggested before, take your time and do the steps in this tutorial one at a time and it won't seem so confusing.
SSD / HDD : Optimize for Windows Reinstallation
After the clean all finishes (step one) type exit 2 times followed by the enter key and the command window will close and you will be back at the installer to follow the steps to a clean install, now it will be good to let the installer do everything.
How to Do a Clean Installation with Windows 7
Don't be concerned with installing any drivers, the Windows 7 installer will do all that.
Avast is good and so is MSE for an A/V, both are free.
Microsoft Security Essentials