Hello, I'm not really savvy with Macs so I'm really lost here. I have an iMac (21.5" late 2010) which when I got I dual-booted with OS X and Windows 7. It's run fine with both operating systems for almost 2 years now. This past week for a school project I needed to work with Snow Leopard instead of Lion, so I partitioned my Lion HD and set aside around 100GB to install Snow Leopard. Since I made the partition I haven't been able to boot to my Windows hard drive at all. When I turn on my computer and hold the "Option" key, Windows 7 is no longer an option to boot to. In Lion when I go under Startup Disk and try to restart in Windows 7 HD, the computer shuts down and when it boots up has a black screen and says "No bootable device - insert boot disk and press any key." In Lion I can still see the Windows 7 HD on the desktop, I can access all the files in it, and I can eject the hard drive. I attached a screenshot of my disk utility if it helps, I deleted the Snow Leopard partition I made so now it's just Windows 7 and Lion again.