I have a hdd with ubuntu (Lucid Lynx) that I use on my samsung laptop. Can I use the same HDD as main (boot drive) on another laptop (HP)? Will it automatically install drivers? Do they override? Is it possible, that it will break my existing setup with overriding my drivers so I can't use it later on my samsung?
Ubuntu is much better in this aspect than Windows. Ubuntu kernel already contains all modules (drivers). So your second laptop must boot correctly. The only exception is proprietary video drivers, I don't recommend install them on second laptop. Open drivers must work out-of-box (but maybe without advanced 3D).