hello, i need to build a development lab where i want to have one ORG with 2003, 2007 and 2010 existing together. i tried to added 2010 but failed with something about 2007 with sp not possible. what is the absolute rule on this. is there OSs and exchange builds that will allow me to do this? i have some systems running with OS's XXXX R2 is this the problem? when building a lab should i be using only OS in "standard" builds and not "R2"? so everyone can live together? what are the details to make my lab work as one?

you should at least have exchange 2007 SP2, installed . you can have earlier version of exchange servers with lastes service pack ie exchange server 2003 sp2 in native modeDhruv

They will happily live together, but must be installed in release order. "R2" has nothing to do with it. Thus you will need to install Exchange 2003, then SP2, plus post SP2 updates. Then install Exchange 2007 SP3 (use the service pack download). Finally you can install Exchange 2010 SP1 (as with Exchange 2007 use the SP download for install). The domain will need to be 2003 native, so that will need to be changed as soon as the domain is created. Simon.Simon Butler, Exchange MVP Blog | Exchange Resources

Sembee, this is good to know will attempt this. i'm starting to download the SP you mention for each of the exchange servers. thanks.