trouble after installation of exch 2 SP3

hi,
We have 2 servers controller in a domain.
After exch sp3 installation, exch services do no start anymore on an installation running exch sp2 since 8 months. Reformatting the hd reinstallating wy2k sp3 dcpromo OK. Now unable to install exch 2000 “a server object for this server (“exchserver”) already exists in the administrative group ….We are unable to find thes objects. Can someone help us.

Somac Luxemburg Europe