Thanks for the replies so far guys. It's not the company laptop; I would rather let Bangalore screw the settings up on that!!! It's my home PC, running Windows 98 and we defrag every month or two, last one done just over a month back.
When you say check the Task Manager, is that just doing an ALT,CTRL, DEL and seeing what is active in the Close Program dialog window?
I am certain it is not the mouse itself as we have an old one which we swapped to test. No difference. Again, at this precise moment everything seems normal, but when the problem happens the pointer seems to lag significantly and it is slow to open new windows etc, including web pages (we are on broadband), which still leaves me feeling it is the system that is causing the bottleneck somewhere.
PP