The following paragraph was extracted from the SDK reference:
In order to truly support NT, GetLongPathName should be dynamically linked at runtime with the proper library.Windows NT and Windows 95: Include an additional header file called NewAPIs.h to make GetLongPathName available on these operating systems. The function is not implemented natively, but by a wrapper that uses other native functions on these systems. For details about using preprocessor directives that make the function available, see the header file. If you do not have this header file, you can download the most recent SDK from the SDK Update Site.
And most important: Does this problem appear only in TeeInstall, or it affects other Tee componnets as well? In case it's just the installer a temporary workaround could be to manually install the components, otherwise a source code change and recompilation would be required.
Iaacov