Clean re-install of Snow Leopard

I read that it is possible to reformat my hard disk and do a clean re-install of Snow Leopard. Are there potential hiccups, for example passwords and will i-Tune remember all the softwares that I have purchased and downloaded on Apple Store?
Doc Olmo

1. Why do you think you need to do this?

2. If you reformat the hard disk and do not preserve your "passwords" etc. they will of course be gone permanently.

3. iTunes (correct spelling) will remember what you have purchased, and in the case of apps will let you re-download it; in the case of music or videos, they won't.

Bottom line: if you don't want to lose your stuff, back it up.

Why do you wanna format, you should never really have to format a mac, unless you have done something that has really messed it up to the point where its unusable (and even thats hard to do!)