Explorer uses 80 - 90% of resources!

After updating recently (20.07.2004), sometimes Windows Explorer uses
around 80 to 90% of the cpu's resources for minutes on end. I believe this
is caused by one of the critical updates as I read something about this at
the time. But of course now I need to know which one of the updates is
causing this problem I can't find the information.
Can anybody help me, or at least point me in the right direction? failing
that I'll have to take to lot out and start again, one at a time.

updates installed:
IE6.0sp1-KB823353-x86-ENU.exe
WindowsXP-KB839645-x86-enu.exe
WindowsXP-KB840315-x86-enu.exe
WindowsXP-KB841873-x86-enu.exe
WindowsXP-KB842773-x86-enu.exe

Sr. Bocadillo