Remove the "MacKeeper" crapware as follows.
IMPORTANT: MacKeeper has what the developer calls an “encryption” feature. If you used it to “encrypt” any of your files, “decrypt” them before you uninstall, or (preferably) restore the files from backups made before they were “encrypted.”
In the Finder, select Go ▹ Applications from the menu bar, or press the key combination shift-command-A. The MacKeeper application is in the folder that opens. Drag it to the Trash. A dialog will pop up asking why you want to uninstall it. You don't have to provide that information. Enter any text in the text box, then click the Uninstall button. All the functional components of the software will be deleted. This is the only worthwhile feature of MacKeeper: it deletes itself. Reboot.
Do not try to uninstall by dragging the MacKeeper icon from the Dock to the Trash.
If you want your computer to be usable, don't install crapware, such as “themes,” "haxies," “add-ons,” “toolbars,” “enhancers," “optimizers,” “accelerators,” “extenders,” “cleaners,” “defragmenters,” “firewalls,” "barriers," “guardians,” “defenders,” “protectors,” most “plugins,” commercial "virus scanners,” or "utilities." With very few exceptions, this kind of material is useless, or worse than useless.
The more actively promoted the product, the more likely it is to be garbage. The most extreme example is the “MacKeeper” scam.
The only software you should install is that which directly enables you to do the things you use a computer for — such as creating, communicating, and playing — and does not modify the way other software works. Never install any third-party software unless you know how to uninstall it.