Item: Windiff.exe utility

Windiff.exe is a tool that graphically compares the contents of two ASCII files, or the contents of two folders that contain ASCII files, to verify whether they are the same.

Resources:
You can find Windiff.exe and various tools included on the original CD-ROM in the Support\Tools folder in Microsoft Windows 2000 and later. 
You can also find Windiff.exe inside Bin folder when you install SDK.

How to Use the Windiff.exe Utility
Download Windows XP Service Pack 2 Support Tools (includes Windiff.exe)
Download SDK (includes Windiff.exe)