Win 2000 server installer and services

I have a server with Win 2000 server installed. It runs mdaemon for email and veritas 9.0 with an HP 40Gb dat disk backup and an APC powerchute. My backup disk appears offline and I can't investigate because windows installer stops responding when trying to install or uninstall software. The services won't shut down etiher. Reboots don't help. Apart from that, all other functions including access to the netweok is fine. Any ideas as to what my problem is guys.

Thanks

George