ya know, someone else mentioned that to me before and i began to rename the file and this danger message came up that i may "damage the file" or something to that affect. I decided to try it again after receiving your message and having a folder full of temp files I could fall back on if I did damage one of the files. I renamed the file, my computer did not explode nor did the file melt as it played nicely to my great pleasure. Thank you John for pushing me to complete that renaming process. Now let me see if I can convert this mpg4 into a DCP file for this British festival. Cheers and Happy Holidays to you and yours.

I suspect you got a message like this:

It seems that the creators of operating systems (at least Windows) are so paranoid about a lowly user messing up something that they are overly protective. It is true that if one changes the extension of files it could have terrible results. A leftover .tmp extension after a process has completed is worthless. Why not convert it to something useful if possible?

As for me, I do whatever I choose to do for two reasons. 

1) Back in 1979 when computers had hexadecimal rotary switches and the registers of the CPU we accessible from a control panel, I watched a machine check stop with a Program Set Hard Error. After looking around in the machine for a mechanical source of the error, a specialist reasoned that the microcode had inappropriately set the error. He then turned off the bit in the error register, hit start and the machine ran fine. The code was analyzed for the defect back in the lab but that didn't mean the machine had to sit in a wait state until the code was rewritten. Since then I've treated all messages with a fair degree of skepticism.

2) I have a bit for bit image of my boot system and my data is backed up in two physical locations.