Your Apple ID is an account used to unify your obtained media/apps/content amongst your Apple devices. You do not need to create a new one for each new Apple machine you buy. Ideally, you'll keep one personal Apple ID for life. If you accidentally made a new ID, despite having all of your purchased content on an old ID, just don't use the new one. Log out in System Preferences, then log into your more fully-loaded Apple ID.
Apple makes removing startup items a more complicated process than it likely needs to be. But if you have some annoying windows popping up on your Mac when you log on, you may need to look in your (often hidden) Library folders. Launch Agents, Launch Daemons, and StartupItems can cause your device to automatically load items every time. Just be careful to not change System files that keep your Mac running properly. Alternatively, check under System Preferences -> Users & Groups -> Login Items tab. You may see apps, files, or folders that open when the associated user logs on.
Jeff would like to know how to speed up his Mac. Leo says to try starting up the Mac in Safe Mode and then go into the System Preference pane to see what's starting up in the background. Jeff can also try zapping the PRAM (Command + Option + P + R). That can make it run faster. He should also browse his System Extensions folder.
Jeff should log into his unused Administrator account and see if it runs faster. If it does, then he'll know something is running in his account that's slowing it down.