WDiff - “file no longer available” problem
LoadRunner uses WinDiff to compare recorded scripts while manually correlating.

I always wondered why WinDiff would throw an error when I invoked it from LoadRunner. It turns out that this only happens if your script directory contains spaces (like the default LoadRunner script directory does). WinDiff is showing it’s age and is not too good with long filenames or filenames containing special characters.

June 7th, 2006 at 8:19 pm
I also came across this problem ,no solution as of now with me but a very best alternative i found.Use Winmerge its a gud comparsion tool low weight on processor and open source so its free.