Not Responding to Quit Request

This past week I?ve had many problems with my HP Compaq Presario Notebook--Windows XP Home Edition.
[1]. I can no longer shut down my laptop the recommended way because the End Program requests get no response from the various programs that apparently run in the background. I have to hold down the Power Button for 5 seconds or longer to turn it off. Is this harmful?
[2]. I can?t open iTunes or Quicktime. The few times iTunes did open for me, the podcasts quit updating.
[3]. I can?t open Microsoft Word -- only the splash window comes up.
[4]. Norton Internet Security: won?t open, and QuickScan does not respond; LiveUpdate tried to download 4 updates but stalled after the first two. Today I tried uninstalling it per Symantec?s instructions but didn?t succeed; it seemed to be in a loop.
[5]. When I try to uninstall the anti-spyware ?XoftSpySe? which I purchased and installed a few days ago because it didn?t respond to a registration request, a message popped up saying ?it?s running. Click YES to close it and continue uninstalling?. However,when I click YES the same message pops up again.
[6]. When I boot up the PC, I get a message: ?Google Desktop Problem_Could not upgrade data base. Try uninstalling.....?.

There may be more but that should suffice.

I?m running out of ideas as to where to turn to. Thanks in advance for your help.
Grev