Starting asterisk

hello sir

Actually when i install AsteriskNow iso file it first wash(clean) the hard disk and then install.
in which mode (graphical / text ) i install it that i not loss my previously install software. i have install (asterisk-1.6.0.1, libpri-1.4.7,zaptel-1.4.12.1,subversion,and all library related it ) my problem is Asterisk iso file
is it necessary to install

Regards:
Shiv kumar
9953956681

digium.com/elqNow/elqRedir.h … 510480.pdf