Reformatting: Impact on EFI?

[Gizmo22]

I have a family member with a Macbook and some as of yet unknown issue. They said they messed up the EFI bootloader by trying to do a side by side install of Windows without using Bootcamp. Now the unit requires several restarts to actually boot into OSx

Does anyone know what this might be? At the very worst, wouldn't a complete reinstall of OSx fix the issue?

 

[Intell]

A complete reinstall of Mac OS X and making sure to wipe the disc when reinstalling will fix the problem.

 

[Gizmo22]

A complete reinstall of Mac OS X and making sure to wipe the disc when reinstalling will fix the problem.

Great to hear as a backup!