Upgrade from Panther to Leopard OSX

I have a MAC running OSX 10.3.9, with specs: Dual CPU G4 1.25Ghz + 1.75GB ram

If I am going to upgrade OSX to Leopard 10.5 (not clean installation), is it possible to do? And if possible, will it give me trouble running applications previously installed on 10.3.9? such as conflicts... or do I need to upgrade the MAC machine to run Leopard?

Any suggestions? Thanks in advance.

just noticed I posted to wrong forum, admin please move it to "OS X - Operating System" forum. thanks!

If you are having conflict problems under Panther, then an upgrade may well carry them over to Leopard. Some applications will not run under Leopard including Address Book.

Your machine will run Leopard very nicely, however an erase of the HDD and clean install will remove all those problems. If you have files that must be saved, consider an external firewire drive and back the system up with SuperDuper.