Install on usb external hard drive

You don't need a special HD. Your laptop needs to be able to boot from USB HD (if it's not 5 years old it probably can). Make sure you install grub on your external HD during installation.

You can make one partition for Ubuntu with ext4 on your external HD and one NTFS for data, where you can put your movies and documents - this NTFS partition will be seen from Windows as well.

You should be able to boot from other PCs as well but you should avoid making special settings (hardware dependent).

Your changes will be saved normally.

I have just tried this on my laptop and it worked perfectly. When I want to boot Ubuntu I chose the external usb hard disk as boot disk. If I don't do anything it just boots into Windows as usual.

There are a few technical considerations of which you need to be aware.

• First, any computer that uses this needs to be able to boot from USB. So you will need to check the BIOS and make sure that the computer is capable of using it.
• Second, unless your drive and computer are both USB 3 capable, the end experience might be so slow and cumbersome that it is only useful in an emergency.

All in all, you'd be better off using eSATA if it is available. I am not trying to discourage experimentation, but an external eSATA drive will be pretty much like using an internal HD and you'll almost certainly be satisfied with the final results.