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#1
MSE is not supported on Windows 8 and above.
Windows Defender have been exactly the same in turns of what they scan and what features they have. Just stick with WD and you'l get the same level of protection.
Having read the OP, they had MSE installed on Windows 7, then upgraded to Windows 10 and the MSE install was kept on there, despite Windows Defender being installed in the OS with Windows 10.
OP is now not able to uninstall MSE as it is clashing with Windows Defender.
To the OP - you could try this to see if it works: Microsoft Security Essentials - Uninstall Completely - Windows 7 Help Forums
Ah - missed that smallprint - apologies!
Looks like it's not good news all round though - Uninstall Microsoft Essentials whilst using Windows 10 - Microsoft Community
Maybe installing another AV like AVG, might sort things out because 3rd party AV programs usually disable MD and by doing that it might re-enable it when you uninstall AVG.