There are times that an uninstallation of McAfee using Windows just didn't get rid of all of McAfee. I recommend using that MCPR tool (McAfee Consumer Product Removal Tool) to be absolutely certain McAfee is gone and won't cause issues when you try to install another anti-virus program. Here is a link straight to McAfee's website. Choose method 2 to download the MCPR Tool and follow the instructions.
McAfee KB - How to remove McAfee products from a PC that runs Windows (TS101331)
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