ooo...
okays. thanks for the helps. ^^
will try it myself as well... thanks a lot everyone. >.<

the most easy way to prevent ur iphone data lost when u format ur pc is by backup or copy the old iTunes folder before formating and put it bec into ur pc after formating, it will keep all ur library as well as all ur data of ur ipod or iphone

i always put my iTunes folder on another partition so that when i format i wont loose my library data, and does not require to recreate and resync my ipod

but then, unwanted plists generated by from previous 3rd party apps will be copied and backed up as well...