Installing applications and Operating System in external HDD

[Guest]

clear steps on how to install operating system and other applications, please?
and my second question is, can i use external hard disk in any computer after installing the O.S. and the Applications?

 

[MrLinux]

Depends on what interface (eSATA/USB) and what OS.

 

[Guest]

Depends on what interface (eSATA/USB) and what OS.

i am using USB. but if information u can give me abt eSATA, it would be so nice too.
but i am to install ubuntu.