Do that right now, before there is any chance your pc gets corrupted and you can't do it later.
New Technology File System (NTFS) is a new way of storing data, I didn't look at the wiki links but I'm sure they'll give you lots of info
Vista was supposed to have a new file system again (WinFS - Windows File System) but it wasn't ready in time for the beta2 release, maybe by the time RC1 is ready or the final release is ready it will be up and running.