Server is getting restarted..

I have an NT4.0 server ..Lotus notes 4.6 Domino is running for Email service..Server is frequently getting restarted as soon as it’s giving message Explorer.exe application error .
I am suspecting Virus on it but i am not able control Desktop.eml files ..even though after deleting continuously it’s flooding.How to arrest this virus ..I am using nimda.exe to clean Nimda worms..help me