Thank you very much hamluis for pointing me to Puppy Linux; I booted from this disk and proceeded to make a backup of Documents and Settings folder on the broken PC. I used an external hdd to store the backup, (It was 29GB).
Now what to do next?
I did a lot of internet research but got very confused. In the end I decided to first of all to replace NTLDR and NTDETECT.com
On my own PC these two files are on the root directory.
On the broken PC they are Not in this directory, (using Puppy). I can only find them in i386 folder.
Is this right? Or shall I put fresh copies in the root directory of broken PC?
Feeling good about this