sorry...hotmail ceased to work for me this week and I spaced on this thread.
Yeah, I guess you have to convert each one...maybe it takes longer than 10 minutes after all, hehehehee...
There's another way to do it, though. Once you've clipped all the files, select all of them [ctrl +A] - then, while they're all highlighted, push the ctrl button. While you're holding down the ctrl button, then LEFT click on any one of the 100 files and pull the mouse over to the right, then let go of the left click button on the mouse. It will make 100 copies.
Now, to get the new material in the first 5 seconds of each mp3, you need to first click on the track where you want it to go, then select "insert" from the tool bar, then "wave from file" and browse to it. It will put the 5 second clip wherever you had clicked before inserting it. If the 5 second file is the same for every tune, here's what I'd do. I'd put it in front of track 1 first and line it up by dragging it exactly where you want it to go (just right click on the little clip and you can move it around wherever you want). Then highlight the 2 files (the 5 second clip and the song on track 1 with the first 10 seconds removed), and go up to the edit toolbar and select "Mix Down >> Selected Waves." - It will blend the 2 together into a new file in the EDIT view of CEP. Then you can convert it whatever sample rate you want and save it. After doing that, then just go back into Multitrack and just use your mouse to move the 5 second clip in front of the tune on track 2. Repeat, rinse, lather, lol.