With OS X Mavericks and Yosemite, you can create a bootable OS X installer which can be used to install the operating system while started from removable media, such as a USB flash drive.
Knowledge Base
Apple Mac OS X Recovery
Recovery System
OS X Recovery includes a built in set of utilities as part of the Recovery System. You can use OS X Recovery to do the following:
- Restore your Mac from a Time Machine backup.
- Verify and repair connected drives using Disk Utility.
- Check your Internet connection or get help online using Safari.
- Install or reinstall OS X.
Why cleaning the Windows Registry does not speed up your computer
The Windows registry is a huge database of settings — both for Windows itself and for programs you install. For example, if you install a program, there’s a good chance that program would save its settings to the registry. Windows would also save pointers to that program. For example, if the program were registered as the default program for a certain file type, Windows would save a registry entry so it can remember that’s the default program.