Yosemite messed up my Macbook. Can I re-install without wiping my memory?

[Jamie Astrix]

The operating system on my MacBook is corrupted and I have important files that I need to recover and am unable to access. Is there a way to re-install an operating system without wiping my memory? I need to transfer files externally so I can access them on a different computer, but my operating system is corrupt to the point where it won't let me copy any files. Thanks!

 

[voyagerfan99]

Boot to a Live Linux CD/USB such as Parted Magic and copy your files to an external hard drive.

 

[Geoff]

What Voyager said would work. I've also installed OS X on an external drive, booted from that drive, and then copied it over to a separate partition on my external HD.