Exchange 5.5 orphaned site

I have a mixed mode Exchange site with no 5.5 servers. I had to forcefully remove my exchange 5.5 from adsi edit. I haven’t removed the Site replication service and the ADC yet. When I try to add a new exchange server the setup fails as System attendent install fails at the point of validating the 55 service account. Can anyone suggest how do I move forward.