Agreed - backups are the way to go. You don't need a backup program, just sync data to an external drive using something like Microsoft SyncToy.
If you backup, I don't see a problem with OS and data on the same drive, because you don't always know in advance how much space you need for each. These days Windows is more like UNIX, in that it tries to enforce a clear separation between the OS and user data, using permissions rather than partitions.
Last edited by bnt; 7th July 2009 at 20:35.