I have a three month old 24" alu iMac running OS X 10.5.1 which has developed a bunch of niggley problems, and this is one of them. I hope someone can help. I have Windows XP installed in Boot Camp, and use Parallels as well. I used to be able to choose whether to boot into OSX or XP by pressing the Option key at startup. However, when I tried today, rather than show the two disk icons to choose from, it simply booted straight into OSX. I can boot XP by change the default startup disk in System Preferences, but the computer simply doesn't respond to the Option key like it used to. I then tried to boot into safe mode (I've never tried this before) by holding the Shift key at startup. Again, it didn't respond to the key press, and it booted normally. I can't get it to boot into safe mode. Finally, I tried to boot from the OSX install disk, by pressing "C" at startup. Yet again, nothing happened, and it booted normally off the hard disk; "About this Mac" in the Apple menu confirmed this. I can't get the computer to boot from the install disk at all. I also tried to select the install disk as the startup disk in System Preferences, but it ignored that too, and and when I rebooted, it ejected the disk and booted normally from the hard drive. So I guess I'm trying to solve a few problems. Why won't the computer respond as it should when I press and hold keys when I boot, and how do I get it to work again? How do I start in Safe Mode, and how do I boot from the OSX install disk? Please help. I'm pretty conversant with Windows, but am new to Mac, so I don't know how to begin to find the problem.