Locks in MAC applications

Hello all,

I have recently bought a mac and I'm really proud of it. I was going through the list of applications available for mac and happened to bump into iConquer. It's a pretty addictive game and I liked it. But I can't pay for it. So, I was hoping I could keep reinstalling once I'm out of the 10 free uses and keep playing. Now, this according to some was not possible( as I read this in the forums ). It seems that even after uninstalling the application and then reinstallaing it, it remembers that 10 uses are over. How is this possible? This would mean there is some sort of file left behind in some other folder. How do I find out about it? It's not that I want to reverse engineer, but I don't want random orphaned files lying around in the system.
Any help / hints in this matter will be appreciated!

Many Thanks in advance,
neokrish