Either Python, PyQT, QT, or Windows Vista is finding my dll, no matter what I rename it to. Is this normal?

I'm experimenting with PyQT, and I was t开发者_StackOverflow中文版rying to figure out how to get it to work with Firebird. I built the Firebird driver, but couldn't get it to work, so I was thinking maybe I wasn't putting it in the right place. So I tried experimenting with the SQLite driver, since PyQT came with it already installed, with working examples. I figured if I renamed all the qsqlite4.dll driver files I could find, eventually the example program would stop working when I renamed the one it was actually using. That didn't work. So I tried renaming the "site-packages\pyqt4\plugins\sqldrivers" folder to "site-packages\pyqt4\plugins\sqldrivers-old", and that did it. The example program stopped working. So I changed the folder name back, and tried renaming all the files in the folder. But the example program started working again. Then I moved the qsqlite4.dll file to a subdirectory, and it stopped working. So I moved it back, and renamed it to blah.blah.blah. And it worked again. Then I opened up blah.blah.blah with notepad++, and deleted some stuff at the top of the file, and that kept the example program from working. So I'm confused. As far as I can tell, either Python, PyQT, QT, or Windows Vista is finding the dll, no matter what I rename it to, as long as it's in the right folder. I even tried renaming it to the name of one of the other dll's, thinking maybe that would confuse it. But it only confused me. Is this normal?

edit: I'm thinking this has something to do with plugins

Yes, Qt plugin infrastructure is a fairly simple and robust one.

It attempts to load every file in sqldrivers directory. If it is successful, each dll then runs a function that registers all the features such a plugin supports.

Then, you application initalizes. If all the features it needs are available, it works properly, otherwise, some form of error or exception handling occurs.