Windows 7 explorer running very slow

Hi
I have win 7 ultimate running on a 4core intel Q9450 and a nvidia 8800gt

Just lately if i do anything in explorer like add a new folder .. move a file to another folder etc it almosts stops! it can take literally a minute or more and the sometimes i have to refresh to see the changes.

I have looked in the rescource monitor but can't see any rescource hogs.

it just seems to run very very slowly.

oh and other programs can be used at the same time and they are as snappy as usual so it only seems to affect explorer.

Has anyone any ideas please

thanks

Mike