I used an old Apple ID to download and install updates from the Mac App Store. I created a new Apple ID for a free iCloud e-mail address. I checked for updates from the App Store and when I tried to sign in, the old Apple ID e-mail shows up in the "E-mail" field and is greyed out, while I can type in the password for the old Apple ID to download and install updates. Is there any way around this? I was thinking of backing up all of my files onto an external hard drive and do a reinstall of Mac OS through the "Internet Recovery" option. Can I log in and use my new Apple ID to get through the reinstall of Mac OS by using "Internet Recovery"? Or, do I have to use my old Apple ID?