Hi, Hoping someone can help. I'm not at all familiar with installing new hard drives and OSX, and I'm just trying to get my mid-2010 27" iMac back in use. The machine was terribly slow, so I upgraded from 4GB of RAM to 16GB. While it definitely helped with speed, it became obvious the HD was failing and a test confirmed so. Recently installed a new 3TB HD (from stock 1TB) and now I need to install a clean copy of OSX onto the new drive. That's where things get foggy. I lost the original install discs. An Apple tech told my brother that I needed to buy Snow Leopard (after checking my serial number) from Apple.com, so I did. I boot the iMac, holding down "Alt" (it's not a Mac keyboard...a cheap replacement from Monoprice.com) and I get a screen showing the disc icon with "Mac OS X Install DVD". Once I click the icon, the drive spins for a second, and then I get the white screen of death with the Apple logo in the middle of it, and nothing happens. I've tried to do a little reading, but this is over my head. I do have a USB 2.0 SATA/IDE HD Adaptor connected via USB, so I can still boot to my old HD, which is now external, but it's really laggy. My brother has been a huge help in getting all of this done and has done all of the work to this point, and he advised me to go into Disk Utility to partition the new 3TB HD, which the Mac sees. I partitioned it with 1 partition, shut down, and tried to boot the install disc again, thinking the machine just didn't know where to boot before, but still nothing. Can anyone PLEASE help?