i have an external for leopard backups, and i see there is a simple folder in it.
is it ok for me to create another folder on the external, and store some stuff on it also?
Time Machine will use as much of a drive as it can to keep incremental backups. You can store other files on the drive. I would recommend partitioning the drive as you see fit.
When you set up Time Machine with a drive, it creates a folder on it called Backups.backupdb. This folder has all of the Time Machine backups in it. You can put other files and folders on that drive. Personally, I think partitioning for the sake of Time Machine is unnecessary because Time Machine doesn't hog the entire drive, you can still store other stuff on it too.
Note: Time Machine works best if you use your backup disk only for Time Machine backups. If you keep files on your backup disk, Time Machine won’t back up those files, and the space available for Time Machine backups will be reduced.
Apple is saying that if you put other data on the drive that cannot be used for Time Machine. Which is true.... So OP, you can choose whether or not you put data on your Time Machine drive, it will lessen the space available for Time Machine, but you don't need to partition it.