windows 7 - Sync file folder on removable device with laptop and desktop

[Recommended questions did not answer my question]

Here is the case:
I have one laptop, one desktop and one external hard drive. I already synchronise my documents and images by means of Microsoft's Skydrive but my Music and Video's folders are too large to do this.

What I need is something that can sync folders on my laptop with files on my external device. Afterwards, when I connect the external device to my desktop, the desktop should synchronise with the external hard drive so that my music and video's are up-to-date on all devices. It would be nice to have an option to select which files to keep when two new sub-folders or files are the same.

Does anyone know a program, utility or Windows functionality (Mac not needed) that can do this? Both laptop and desktop run Windows 7 (laptop 32 bit, desktop 64 bit).

EDIT: Since both the laptop and the desktop are connected to the same LAN, it's also possible to let them sync via the local network. That would be even more perfect. I don't want it to sync over the Internet (would cost too much time and download/upload) but over LAN should not be a problem.

Answer

I'll throw Microsoft's powertoy SyncToy into the mix. It can provide some nice functionality without getting too over the top with some features you may not need. Also you can use windows 7 and task scheduling to customize when to sync (maybe detect when external drive is connected?). Using this method, you would have to separately set up the desktop and your laptop, but that could also give you some added flexibility.

Here is an article going through steps to automate synctoy (link)

Good luck on your search.