Why a classic ASP can write to a folder which has no write permission assigned

HI,

I have moved classic ASP from IIS 6 to IIS 7.5 on windows 2008 R2 to run, and study that now IIS 7.5 uses AppPoolIdentity to control access to folder resources, however, I follow steps on create an AppPool, let's says named ClassicASP, and then add "write permission" to folder D:\doc with "IIS AppPool\ClassASP". THe ASP works fine and can write to this folder.

But surprisingly, I remove "write permission" of "IIS AppPool\ClassASP" from the folder, the ASP can still write to this folder.

Finally I remove permissions such that only "System" and "Administrators" have left to write to this folder, the ASP can still

write to the folder.

I really have no idea what is going on. Is the "w3wp.exe" running as System account ?

I use process exploer to check and seems not possible to have "system" privileages on w3wp.exe

Does any professional get me out of this question?

Thanks in advance,

Ray