a quest for difference

I'm looking for a good, free, visual Diff program for Windows. What I need from it is:

• Small + no install needed (the preferred is one executable file which I can drop wherever I want).
• Allows to drag-n-drop files into it (fast use)
• Has refresh
• Allows to copy-paste from it
• Nice coloring to find differences quickly

As simple as these requirements may seem, I have a problem finding such a program. At workplace #1 I have the great Tkdiff, but it requires a Tcl/Tk install which is not something common on Windows machines.

So what does one like me do in such cases ? Right, start thinking about rolling-my-own :-) I actually did some research and see it should not be too hard.

Last week, however, I found WinMerge. It is quite good, with just two things lacking: the Refresh doesn't work, and the coloring is a little unsatisfying (the whole line is always colored, regardless of where the difference actually is inside the line).

I'll try to contact Winmerge's developers or get hold of its source (it's GPL, I think). If I won't suceed, I might get to writing my own anyway, once I get that RichEdit control to work :-)