Re: black screen on bootup
If you have the ability and patients, uninstall all applications that you run in a typical day. Everything from games, to utility programs, to applications like Quicken.
If you have the patients do this one application at a time, then turn off and see if the computer does the same thing. Then uninstall another app, so forth and so on.
BEFORE this see if there are any options in your BIOS about halting on startup incase of error or something of the sort.