I upgraded to Mavericks last month. Things ran fine at first, but then my Macbook seemed to be slowing down and freezing up every other day. It started doing this again just now. I restarted since nothing was responsive. The machine took longer than usual to boot up, and when it finally did I was greeted with the OS X Utilities screen. I tried running Disk Repair and got some message about EFI partition map needing repairing or something. Using my brother's laptop I Googled the problem and found out this is some kind of bug with Mavericks. I tried to reinstall the previous OS I had (Snow Leopard) but no HD will appear when it asks what I'd like to install onto. I decided to try running Disk Repair from the installation disk and got a message about B-tree node size and that the disk cannot be repaired. Now the Snow Leopard disk doesn't seem to want to eject from the Macbook. I don't have any files backed up. I have over 700 songs downloaded and I'd really hate to lose them, but it seems like there's nothing I can do to save my files. Am I completely SOL and need to get a new MacBook or is there something I can do to save this thing, even if I have to lose what's saved on it?