rebuilding a prel file in PE 11 and AVI files won't import now but did in the original edit session

Reinstall the program and start your project from scratch.

I'm assuming that, after you updated to Windows 10, you installed Premiere Elements 11? Don't know that I did that. I believe I updated to W10 thru download but did not reinstall my programs. If that is something I would have had to do, it is just that I don't remember doing it.

A hard drive crash is a major event. You really have to pretty much rebuild your operating system and program installations -- especially since you compounded things by also changing your operating system. It wasn't thr hard drive, everything was on a back up drive that failed. I sent the drive to the mfgr and they captured as mush as they could and put on a new external drive. So, many of the files of the original video are there, but it appears the avi files I created by editing certain interviews outside the main project and them importing that edited file are the avi files I cannot import now.
 

That will solve your codec issues. (That's certainly not a Windows 10 issue, if you're working with DV-AVIs and MP4s -- though it's possible your AVIs used other codecs which may have been wiped out.) (that's what I wondered if the codecs that were originally installed with PE11 were wiped out when W10 was installed? I am not all that up to date on the newer things. I first stated using computers about the time of the Atari 64.

As for your old project, there's really not much you can do about it without your media files. I have loaded the prel file from the original version. It has some graphics, titles, background music and one or two short pieces of orignal imported video. All the interviews that were edited in their own prel files and then output as avi's are not in the new "recovered prel" file. If I can figure out how to import the avi files, I can rebuild it with minimal effort (I hope)

I'm assuming that, after you updated to Windows 10, you installed Premiere Elements 11?

A hard drive crash is a major event. You really have to pretty much rebuild your operating system and program installations -- especially since you compounded things by also changing your operating system.

That will solve your codec issues. (That's certainly not a Windows 10 issue, if you're working with DV-AVIs and MP4s -- though it's possible your AVIs used other codecs which may have been wiped out.)

As for your old project, there's really not much you can do about it without your media files. You probably have to throw it out and start with a new project.