Running BDS2006 and RAD2007 on the same PC (http://www.sandon.it/node/23)
The "non-breaking" release RAD2007 has the nasty habit to break an existing BDS2006 installation because packages - including those used by the IDE - have the same names, and usually the RAD 2007 path comes before the BDS2006 path - and thereby BDS2006 attempts to load the wrong packages.
A workaround is to use DLL redirection (http://msdn2.microsoft.com/en-us/library/ms682600.aspx), a feature of the Windows loader that allows to load DLLs from the application path first, ignoring the path.
Just add a bds.exe.local file in the BIN directory - it can simply be an empty text file renamed - and BDS2006 will load the BPLs from its own directory.
Codegear could have used isolated applications and side by side assemblies (http://msdn2.microsoft.com/en-us/library/aa375193.aspx) too, which is a more sophisticated technique to run different DLLs with the same name.