Among the symptoms/problems:
Computer takes 5-10 minutes to boot, and the hard drive hits constantly throughout startup.
Norton Internet Security does not enable itself, even though it is optioned to do so. It will enable manually, however.
Half of my Control Panel icons have disappeared in the classic view, including Power Management and Display.
Windows Defender program gives error message on startup and won't launch (I tried updating it when I learned the old program expired a few weeks ago, but update didn't take, so I uninstalled the whole program).
When trying to come out of hibernation, only a black screen and cursor appears.
Once everything finally gets up and running, things seem to be fine, although the computer has locked-up at times when I try to do too much too fast.
That's all I can think of now...I have tried my usual scans (Norton Anti-Virus, Ad-Aware and SpyBot), defragmented the hard drive and tried System Restore to two earlier points, all to to good end.
Thanks for any and all help.