Format disk?

what will happen if i use the "format disk" in the setting-system-System Re... Folder

is it possible to reinstall all the windows and fw etc?

It doesn't format the whole disk - just the contents of the disk folder. So you don't need to.

You can format disk and then reset registry and then do a fw upgrade and that would be as close to a 'full' new installation.

You can access the fw directories when you connect via activesync... i am not sure if it would be a good idea to format that directory (even if its allowed), but if you have some ghost folders in there you could possibly get rid of them from there.