slow shutdown

I had intended to address this problem in a previous post but got sidetracked. I have an NT server, nothing special on it other than the NOS. It has a primary 3 gb C: drive and a slave D: that is 6 gb. I now notice that shutdown is very slow. It takes up to 3 - 5 minutes to shutdown. I can not be more specific since it occurred so suddenly and I have no clue why? the only things I have done is (1) install more memory , from 64mb to 96mb and (2) try to install a video adapter/driver to improve the video resolution. It originally had a mono monitor and now I've got a color and wanted to use the full capability of the onboard video but I haven't been so lucky so far.