Well... all of that is not so easy to explain, but sure I'll try to do that.
I bought a new computer 1 year ago, with quadcore, 8Mb memory, 1Tb HD, big screen card,... and so on. It's a nice machine.
My OS is Win7-64.
Never a problem till this week.
The problem I have to fix:
On wednesday, my computer announced me suddenly that it had encountered a disk problem, with recommandation to do a back-up of all my files and the system (done). I first tought it was a virus attack coming from the Internet.
What I've done till now:
1° Tried to do a scanning of my data's, but it couldn't do it. Tried this 4 times with same result: impossibility to end it and allways same announcement of the computer: disk problem and backups to do.
2° I have then tried to do a check disk, but again the same problem: blocking of ongoing work and the computer warning regarding a problem disc.
3° I phoned to my computer reseller whos invited me to go and search on the Internet for UBCD; to download it and to copy the downloaded file on a CD. Then I'll have to restart the machine with the CD in the drive and a menu will appears. In this menu, I had to scroll down to "Diagnoses", to select HDD, to click on "VIVARD" and then on "test & remap".
Following his explanations, that would do a special check ok my disk and try to repare it or to find what's really happen.
4° I did what he said me, but could not start "on" the DVD I had prepared.
5° Due to this problem, I took then contact here thinking it was because I was using a DVD rather than CD, quod non.
And
now, I try to follow your advice and guidance.
5°-sub1. First of all, I've controlled if my bios was correctly configurated (in other words: could my computer boot first on the CD/DVD?). To verify this, I opened the Main control panel and choosed the subfunction "Save & Restore", and then "Create a repair disk" (when trying, the computer could well boot on this DVD > 1st control O.K.).

what gave this
5°-sub2. I went and read and followed the tutorial you advised me:
this one. And now, there I am: this tutorial explains the need to customize UBCD disk at my own situation in order to make it bootable
see here. And at this step, I completely lose due to ununderstanding the indications > how to do it?