Actually - I did System Repair from installation DVD it did this:
- it deleted profiles of existing users, and data in Documents, Settings, Desktop,... all lost
- programs were left ok, unless they did have some data connected to specific user profile !! be carefull !!
- you'll lose personal certificates in IE (be it for bank, accessing some sites,...) - since they are connected to user profile.
Oh! yeah: the graphic drivers
were also gone....
- sound, mb, ok. (??)
I made a export of certificates and put it on a flash drive, but it's lost (so...) - argh!!!