Delete command not deleting files in Windows directories

[jwptrek]

I am having a problem where my uninstaller is not deleting files properly from Windows folders.

The commands are (I've put some placeholders in for confidentiality):
Delete $WINDIR\system32\[filename].dll
Delete $WINDIR\sysWOW64\[filename].dll
Delete $WINDIR\system32\drivers\[filename].sys

My current suspicion is that the DLL files are in use by a different driver not just mine, since they are API DLLs. The sys file is only for my driver, however, and I know the driver is being removed from Windows. It doesn't get deleted either. However, the uninstaller gives no error when it tries to delete the files.

I am going to run the installer and uninstaller on a clean boot machine to see if I get different behavior. I was hoping however that someone would have ideas to make the files delete properly