My Envrionement consists of a Server 2003 SP2 (DC, AD, GC) that has checked out successfully with DCdiag utility, the Server 2003 is also running our company exchange 2003 as well (mixed mode that I will change to native) server is about 6 years old. it has limited harddrive space availalbe, the C:\ is about 550mb the d:\ dirve that is home for the exchange store is 2.50gb. Would like to transition our current exchange server to 2010 Exchange (have new hardware, installed server 2008 R2 (64bit). The 2008 server that is going to support the new exchange 2010 is already joined to the domain. I would like to also move the DC and AD responsiblity to another new server that is Server 2008 R2 (32bit). I was informed previously not to move the DC to another server until I transition the exchange to the new 2010 server or I could experience a lot of issues with the current exchange 2003. My plan is to transition the 2003 exchange to the 2010 exchange first. My concern is how much space will the schema upgrade take on the 2003 server AD, do I have enough space to accomodate the changes in the 2003 schema for the 2010 exchange (there is about 20 users on the current 2003 AD). Is this the proper global plan I should follow: Exchange 2010 transition and then 2003 DC (AD) to 2008 DC (AD)? The old server 2003 will be dpromo and removed after this full process is complete. I assumed this to be strait forward but do not want to take anything for granted knowing that any changes made to a Schema should not be taking lightly. Any Thought is welcome.