What you need is a program called HJSplit.

What is HJSplit?

HJSplit is a popular set of freeware file-splitting programs created by Freebyte.com.

Now what’s the use of a program like HJSplit? Think of a file of 20 Mb, and try to send this to a friend. Using email this does not succeed, it is simply too large, and how to put it onto a floppy? HJSplit will enable you to split the large file into smaller chunks, which can be much more easily sent and stored.

Of course HJSplit can join these split parts back together again, so that the original file is restored. Alternatively, you can use HJJoin for this, which is a tiny and specialized program for joining files.

HJSplit is very reliable, simple, small and easy to use. It does not need any installation or complicated DLLs, it just consists of one ‘.exe’ file.

Here’s a nice HJSplit video tutorial which will run you through a quick example of how to join files.