Applications take forever to start up

I am running an NT network. On one of my client computers I installed Internet Explorer 5.5 with Service Pack 2 to accomodate this new nimba virus. I also installed Service Pack 6a for high encryption and the security patch over this. Since doingso, only on this computer, the user finds that her applications (especially Excel) are taking forever to load. They are not responding immediately to the mouse click and even closing down can take forever. Can anyone help with this. I haven’t come across this yet and I wonder if it is what I have installed has caused this as the applications were running acceptably well beforehand.

Regards

Debbie