Have an XPS400 running WinXP, service pack 3.  Computer is hanging in following way, typically after running a while with several applications open: 

With various software running (Office, IE, doesn't seem to matter what), when I do a left mouse click the cursor changes from pointer to hourglass afterwhich the PC will hang.  Pressing any mouse button or keyboard key does nothing; although I can still move the mouse cursor around.  Doing CTRL-ALT-DEL has no response.  Only choice I have is to turn PC off.

Event viewer does not show anything unusual.  Does not appear to be connected with what software is running.  Don't remember this behavior being connected to any new installation.  I am trying to pin down whether this might be software or hardware.

Any thoughts?

Walt