Thanks everyone for your help, that was great. Good to know there are always people ready to bring help
So after 3 full days of researches and different tryouts, I finaly repaired my computer all by myself.
Here is the way I made it, for those who shall have the same problem :
First off, the problem really came a partition problem.
As I said before, Partition Magic is NOT compatible with Windows Vista. So my hypothesis was right.
Impossible to restore, to repair or whatever since Windows couldn't find any OS installed, the partition had just disappeared and it was as if there was no OS installed and ready to boot on the computer.
I've tried Vista CD, even Win7 CD, even WinXP CD, none of 'em found any OS installed, so nothing to repair.
Tried all these 3 Windows OS CDs to try a new OS setup straight from boot sequence, none of them worked, error message everytime : partition damaged, no free partition to use.... tried to use the format tool, didn't work.
My solution :
- I finaly found a way to start Ultimate Boot CD (thanks very much, great f***** GREAT program !!!! but tough to master) ;
- Started PTTD to format one of my unused partitions, clear it up and make it ready to host a new OS (format it in NTFS) ;
- Started Parted Magic to use TestDisk (thanks very very much to this great software as well !!!!!!!!!), to clean all my partitions and write new Partition Table (which was screwed and cause of issues) ;
- Ran Win7 CD at boot sequence to install it on my freshly formated partition, everything went fine ;
- Ran Win7 to save all my datas on my HDD (in case something went bad afterwards) ;
- Ran cmd.exe (admin mode) and made a chkdsk /r on my Vista partition (took several hours) ;
- Rebooted computer, then booted Win7 CD to get in recovery mode (repair), initialy I wanted to make a bootrec/fixboot, but finaly I could see my 2 OS appeared properly so I clicked on the button to repair Vista's boot sequence ;
- Rebooted, IT WORKED !
Hope this helps.
Once again, thanks again for this great UBCD program that saved my computer (even if it's very difficult to use it, so many programs and we don't really know how different they are, what are the ones adapted to the current situation...) and also thanks very much to Parted Magic & TestDisk which are very complete, simple and powerful programs to use.