recover an account after restalling the linux system

I have a laptop with ubuntu installed before. Recently I changed to install mandriva, at the same time conserving all the previous working files (data, documents etc). There were two accounts in the ubuntu system, after the change, I can not log in the other account. When I check the system, all the folders are still there. So I just
sudo adduser username.
Then specify the group of the user. This can be done either by modifying /etc/motd, etc/passwd and /etc/group; or go to the control center of mandriva linux and modify the user information.

Afterwards the other account is recovered and I can log in !