CNSHOOT.DLL error

I am using Window ME for years and it is working well until
last week. I can log-in to ME and all the programs are
still functioning but the Internet Explorer and the file
manager as I got CNSHOOT.DLL error when I trying to using
these two. Maybe I think it would be caused by virus since
the problem happened just after I download the MIDI music
from web. I use PC-cilli to scan for virus but it didn't
help. Could anyone here give me a help otherwise I think I
need to re-install the Window and see whether the problem
can solve. Also could anyone one can advise that when I
re-install the Window ME once. All the softwares that I
have installed before will be kept or be overwrite. I have
installed a lot DV editing software there that may need
more time to re-install all. If the problem still here even
I re-install ME than maybe I have to format the harddisk
first Am I right. I look forward to your help ASAP.