Posted 01 August 2012 - 06:55 PM
Can you install to an external? Yes. Nothing to stop you. If the external drive is fast enough (at least USB2), and if it's a real hard drive and not a flash drive, it will run almost as good as if it was installed on the internal drive. (Flash drives work, but won't be as fast. The advantage is you can carry them with you if you're willing to lose some speed.)
However, if you do use an exteranl hard drive you must use the linux bootloader. You can use a Windows bootloader to load linux and vice versa. But Windows isn't smart enough to boot an OS from an external drive. At least, it wasn't the last time I tried it, and I doubt that it's changed. There are exceptions to that "always" rule. But they sometimes aren't straightforward.