Make a long story short, SWAT model actually is a plugin that was developed by a team from swat.tamu.edu. The open source plugin runs with proprietary ArcGIS system. Then another group from MapWindow.org made the same plugin that runs with MapWindow. The other problem is, it only runs on Windows :-) (well this is actually Mac and Linux User's problem). Therefore after this one, I will look up a similar plugin to Quantum GIS, which runs on both unique OS.
It is very useful for people and students that mostly can operate ArcGIS from their office lab or university. But it kind of has different kind of workflow and dependencies files. One must keenly follow the tutorials from both versions. This is what I'm working on.
Hopefully soon I can post the result, based on Cikapundung catchment dataset.