Program stop

In the past few day I've been having programs stop responding in the middle
of my work or when I try to activae it. I wind up sending error reports
after error report to Microsoft or rebooting my system in order to get out
of it. I try ending the program in task manager, but sometimes that freezes
up too. Could someone shed some light as to why and what makes this happen.
I have not made any major changes to my computer in the last few months.
Help........frustrated.

Windows/xp home w/service pack2
Norton Internet Security 2005
--
Thanks, Phil
.