concat

ConCat/Split is a Windows Explorer context menu extension that provides two complementary facilities:

1. A split facility that lets you easily convert a single large file into
several smaller ones. You can copy these smaller files onto floppy
disks, or send them through email facilities that will not cope with
large files.

2. A file concatenation facility that performs the same operation as the
command line "copy /b SrcFile1+SrcFile2 [+SrcFileN] DestnFile"
operation. With ConCat, you can append any number of files and store the
result as a new file, or overwrite one of the original files.