Question: VB6 came with `WinDiff`.

Is there a free modern version of WinDiff available that is able to ignore case?

Answer: 
Along with WinMerge and the WinDiff from the latest SDK, I also have SourceGear's free DiffMerge.

I use WinMerge (which hasn't changed for a while either -- don't ignore blank lines; that exercises bugs) most, especially its ability to open two blank editable pages and you can paste anything, such as from a Remote Desktop to a machine that does not have any visual diff installed, and the differences automatically (or manually if you prefer) update.

DiffMerge's feature I like is its display of differences, which seems to cater for spuriously different line breaks better.

And, to answer your question, the WinDiff from the latest SDK (or at least the one included with Visual Studio 2010), WinMerge, and DiffMerge can all ignore case.
WinDiff is part of the Windows SDK, it still ships with it. But no, the SDK is targeted to programmers that write code in case-sensitive languages, C and C++.

The source code of WinDiff was once part of the SDK samples. You can still get it from [this web page](http://www.grigsoft.com/download-windiff.htm), assuming you're into hacking C code and have an old compiler laying around. You'll need to adapt line.c, the line\_gethashcode() and line\_compare() functions. Lower-casing the line is easiest.

Well, that was the programmer's answer. Plenty of other fish in the sea, Beyond Compare typically gets a lot of nods.