By default the location of the project '.bld' file will be inside the <setup> folder of the project folder.
When project '.bld' file is saved in to other folder due to any reason, the original location with the files must be there in tact and the project '.bld' file will refer to these files.If by any reason the project folder is to be copied in to other drive, copy the folder in to the root of the selected drive and the original folder has to be renamed or deleted to prevent the '.bld' file to make reference to earlier.