well, i think i know what's wrong now. my computer just crashed and then rebooted really quickly--like five times. then it started up normally. a warning icon appeared on the taskbar and let me to the System Log. i got this message:
The file system structure on the disk is corrupt and unusable. Please run the chkdsk utility on the volume C:.
For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.
I did some googling and apparently this means my harddrive is corrupted or something. does anyone know about this chkdsk utility and/or what to do?