WinInet - Can Http Connection be made that uses Windows Auth. Username/Password?

I'm writing code that will connect to an Http server. The user may want to use a specific Username/Password and I've providing a UI so he/she can enter them. But they may alternately want to use the Windows Authentication Username/Password that they have already used to login to Windows. Is there a way in WinInet to do this? I've spoken to colleagues who think that there is, but they don't know exactly what it is. I've just ordered a WinInet book from Amazon, so maybe my answer will be in there, but if someone out there already knows, please help.

Thank you,

Rob