Hello John !!!
Thanks so much for being so fast and helpful !!! I'll check the links and I'll let you know =)
Let us go through this systematically to see if we can get at the core of the issue. The answers should be in the details.
Given that you are using Premiere Elements 11. You say that you are using "Microsoft XP". Is that Windows XP Professional SP3 32 bit or something else. Whether it be 32 or 64 bit, your Premiere Elements 11 is going to be a 32 bit application and as such has the limitations of 32 bit system that being maximum supported installed RAM = 4.0 GB of which typically 3.0 GB or less of that are available. That and your free hard drive space needs looking into since you say that a 2 min project works and a 40 min project does not. So, we need to assure an optimized computer with adequate available RAM and free hard drive space as well as Scratch Disks directed to a hard drive area with enough free space to accept as they are automatically generated by the program in one of its operations. Do you have pile up of preview files and conformed audio files in the Adobe Folder that needs deleting and/or a pile up of conformed video that can be cleaned out in Edit Menu/Preferences/Media.
You cannot move or delete source media that went into the project after the project is saved closed. When you re-opened it, you will be hit with some nasty missing media messages. But those messages will be your avenue to reconnecting the missing. If you are not moving or deleting photos and you are storing them on an external hard drive and using them from there,
a. make sure that the external hard drive letter is not changing
b. make sure that the external hard drive is formatted NTFS and not FAT32
As for your message
"Error compiling movie. Unknown error"
Expand the Timeline with the -+ slider over the Timeline to get a close look at the track content. First look for very thin vertical black lines that may be scattered on the tracks. They must be deleted if there. Look for irregularities in place of transitions, gaps, etc.
Define the properties of what you have on the Timeline in terms of formats including file extension, duration, effects. This all may boil down to breaking apart the content in search of offending component(s). You mention that this 40 min Timeline consists of
videos, sounds, musics, jpeg images and screencaptures
Those screencapture formats draw attention.
What are the pixel dimensions of those photos and how many of them do you have? Another attention grabber.
When I refer to formats, I am typically referring to video and audio compression, frame size, frame rate, aspect ratio, file extension, duration. Are you working from an NTSC or PAL setup?
Please review the above.
If you need clarification on anything that I have written, please do not hesitate to ask.
Dear John and Romano,
Thank You so Much for your kind answers !!! =)
My project is damaged. I will have to start it all again, using this project as a reference.
I will use After Effects to make the new project; and this time, I will do Scene by scene, and this way it will be much easier to encode.
I can not open two Premiere Elements windows, that's actually why I think I will use After Effects, this way, I can open Premiere Elements and After Effects at the same time.
Thank you So much for your answers.
Have a Great weak and a good monday,