Hi All, I am writing a 64 bit class library hence I assume I need to use 64 bit compiler ( csc.exe ) I would like to know how can I configure Visual Studio 2005 so that csc.exe present in C:\WINDOWS\Microsoft.NET\Framework64\ is used instead of the csc.exe present in C:\WINDOWS\Microsoft.NET\Framework\ which i assume is the 32 bit compiler - Rakesh