The following blog post of Long Zheng explains the details about Microsoft's Ringtones folder:
You see, I thought we had all learned a lesson with the Crazy
Frog and ringtones based entirely on repeating single-syllable
words, but apparently not. BingTones are now invading public
places around the world. In a bid to maintain social order, I come
offering some ringtones from Windows 7.
As part of Windows 7′s new foundation for managing communication
applications at a system level (for example, lowering the volume
or muting your music when you receive a call on Skype), the
operating system actually now ships with ten soundclips which can be
used as ringtones, stored as WMA files under the
%ProgramData%\Microsoft\Windows\Ringtones” folder, for your
There is of course nothing stopping these ringtones from being also
used on a mobile phone.
I'm also copying the text in Microsoft's link in case of link rot:
Windows 7: Building Great Audio Communications Applications
Using the PC as a phone is central to the future of communications,
and this session will provide you with the essentials to build the end
to end experience. Windows 7 provides APIs for integrating
communications capabilities into your applications. This session
covers attenuating and muting sounds during a phone call, receiving a
phone call using a Bluetooth headset, improving the latency of a phone
call, and selecting the appropriate communications device.