What is it?

stisvc.exe is? a still image device?service that is part of windows 2000 WIA software

What does it do?

Windows Image Acquisition (WIA) enables imaging programs, such as Microsoft Picture It! 2000, Kodak Imaging, or Adobe Photoshop, to communicate with imaging devices such as digital cameras and scanners.

More info:

http://support.microsoft.com/default.aspx?scid=kb;en-us;266348