Folder Owner deciding factor in Windows

Hi ,

I logged into my windows 7 system with admin previlages and created a folder and i see that the folder is given owner as "NT AUTHORITY\SYSTEM" but instead of that i want it to be my username. And sometimes when i create the folder it creates the folder with owner as my "username".

I also observe sometimes it assign's the folder owner as "BUILTIN\Adminstrators".

Please give me the infromation on what basis Windows assign the owner of the folder.

Thanks,

Chandra.