I'm running a MacBook with Tiger. Okay, this is a many-tiered problem. I was stupidly running Software Update on a full hard drive and my computer crashed. After this I got the blinking question mark screen. I brought the computer to the Genius Bar and they somehow brought the system back without having to erase the disk. There was a "Previous System" saved but after two weeks of smooth sailing I deleted the archive, since it was taking up a huge portion of my disk space. I was running Final Cut Pro and noticed that Compressor was suddenly grayed out. I can't run Compressor - it doesn't even appear in the dock when I try opening it. Also, a number of my Quicktime codecs (Uncompressed 8 and 10 bit, for instance) stopped working. Final Cut tells me they're gone or have suddenly become incompatible. Someone on another forum told me to "downgrade" Quicktime to 7.3.1 using Pacifist. However I was already running 7.3.1 so I tried downgrading to 7.20 instead. After doing this I could no longer open the Quicktime player or preference pane. When I tried playing videos in the Finder it would crash. I tried reinstalling Quicktime 7.3.1 and restarted the computer. Now my user account folder is missing, the clock is missing, Quicktime crashes, Finder crashes, Quicksilver won't open and System Preferences crashes whenever I open it. Firefox and Safari also crash. Software Update crashes. Everything is running very slowly, too. I moved all of my preferences to the desktop and checked permissions and all of that jazz. Nothing has an effect. I can't create a new user account because the preference pane crashes. I lost my OSX install disk. Oops.