On Fri, 15 May 2020 at 06:21, jon.ingason@telia.com <jon.ingason@telia.com> wrote:
I have computer which I build for 13 years ago. I have just replaced the battery on the motherboard and could restart
the computer and everything worked OK. The I needed to restart the the computer again and it did not boot from
the hard drive. I could start it from SystemRescueCD and the file systems where OK, fsck on them all where OK.
From that I conclude that it must be the boot partition that is corrupted.
How can I fix the boot partition?

Was there some event you think caused the problem?   How old is the hard disk?   Before 
spending time trying to recover the system, you should run some disk diagnostics.   If your 
drive is old and you don't have a good backup you might be better off copying important 
stuff from the old disk to a new disk.

You may be able to get a CD image from the drive's vendor (assuming you can figure out what company 
has support for your model) and you can install the smartmontools from a live boot and run the long test.   

 -- 
George N. White III