How much hard disk space does LyX need?
The LyX binary consumes about 2.0 MB of disk space, while the supporting files occupy another 12.6 MB (9.1 MB of which is consumed by the docs! You can delete the languages you don’t care about to save some space). Of course, you do need to have a LaTeX-compiler, e.g. teTeX or MikTeX, installed. This consumes about 115 MB, as well as ghostscript, which is another 10 MB!