"For compilation, I added x64 target in VIsualStudio 2005." - I didn't do this. "Do I need to set any compilation flags?" - I didn't set any additional flags. " Is it mandatory to compile it on 64 bit machine itself or compiling on 32 bit machine with x64 target is OK?" - I build pjsip on x64. And build be possible to run on x64 (tester's PC) and x86 (XP Win7 customer's PC) -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.pjsip.org/pipermail/pjsip_lists.pjsip.org/attachments/20121001/523ad206/attachment-0001.html>