The original poster describes a way of working that sounds similar to
my own. I tend to work at stuff on an office computer, and away from
the office on any one of three notebooks. I transfer folders between
these computers on a USB memory stick.
The possibility for getting mixed up, and not having the right file on
the right machine, is huge. I've found Andrew Cutforth's AJC Directory
Synchroniser (http://www.ajcsoft.com/index.php) invaluable. I much
prefer it to Windows's built-in Suitcase synchroniser.
Once you've grasped how to use it, it's pretty simple. I recommend it.