hey i got fatal error when launching hpl editor

[Mudbill]

Unless your Mac already came with an earlier version, you'll have to actually buy a physical disc to install it. It also involved reformatting the hard drive, which erases everything on it including all your documents and files. I don't necessarily recommend anyone to do it; best someone with experience.

If your Mac DID come with an earlier OS X version, you can reformat to the factory OS using Internet Recovery. You won't need any discs, but you'll need an external USB Recovery Disk to actually run it from in order to get wipe-access to the HD.

An alternative is of course to use Boot Camp to install a Windows partition on your disk. Doing so you can switch between running Windows and Mac OS X by restarting the computer.