Hi ppl, My application runs in WinPE2.1-x86, but the same application's 64 bit build doesnt run in WinPE2.1-x64. Is there any size limitation in WinPE-64 bit OS. My application is 550KB. Is there any special project settings for making the application launch in WinPE-x64. (loading dll) I use runtime library:MT, Use of MFC:Use standard windows library, common language runtime support:No clr, DEP: default, Randomized base address:default etc. I use 'SDK for 2003' for building 64 bit application. Should I use 'SDK for 2008'. But a helloworld program built in SDK 2003 works in winPE2.1(VistaPE). thanks in advance Kararu.