Thanks, xtacydima. But I am actually looking for a way to measure transfer rate of a file on a hard disk. I have this 800MB file that causes DVD burning at 4x to slow down near the end of the file. I don't know why but if I copy the file to a new name on the same hard disk and use that new file then everything is fine. It could be that the hard disk needs to be defragmented but this is only 4x burning speed which is 5MB/s! When it slows down, the Nero buffer shrinks from 100% to 0% and the real-time speed display reduces from 4x to 1x-2x. Check out the screenshots. Watch the User read buffer and Writing speed near the end of the first file where it's struggling under 2x (from 35%-50% of the whole progress) and compared with the second file.
What could be wrong with the first file? Both file are identical and have the same MD5 checksum. That first file caused bad burns because of that problem near the end of the file. That's why I wanted to see the transfer speed graph of the file.