It is sure a very helpful software and makes our work easier and comfortably simple. Sometimes you might have been wondering, where IDM is keeping your files before producing the final output you get after the finished download. Well, it is simple - Your files are unfinished and it should be in the temporary folder. Once you hear about it, You are almost there.
IDM saves your files at this location :
You will find folders which is indexed by the names of your current unfinished downloads. You got it now. You can wander around a little bit and get to know that files have no extension on it.
If you are downloading multiple files at once - like music album - you'll find that there are exactly the same amount of files without extensions. To get the preview of the files, you can copy one of them to other location and add an extention at the end.
Play or open the file with the software which can run it.
*Never rename the folder or file you are download in the temp folder of IDM or you might end up with the un-resumeable download.