After several backups, I downloaded OS X Yosemite, Public Beta on my early 2008 MBP with OS X 10.93 and a OWC SSD and 60GB of free space. Mac acted a little strange after download, desktop opened slowly and was grayed out with a bright window asking if I wanted to install Yosemite, unfortunately I said yes. I can't get the MBP to boot either in Yosemite, or Mavericks on a tested USB HD, or with the original Snow Leopard DVD. No response from the screen or boot sound, black screen. 1. Apple support says the screen has failed, but left side of MBP gets hot and no fan noise. Bootable USB HD lights up but does not respond. Boot DVD spends up but does not load, Black screen. 2. OWC says I should remove the SSD and try to boot from the USB HD or DVD, will try tomorrow. This SSD has worked great for the last ten months with Mavericks. 3. Apple service tech says I should try a DVI monitor, but without drive noise or boot sound I don't think this will work. 4. I have tried a Network boot, all the startup hold keys, and removing the battery for a cold start. Does anyone have any ideas or recommendations? I been using MACs since the mid '80s, but this is the first problem I haven't been able to fix.