After a power failure when I tried to boot my FC4 computer it started to scan my file system automatically and after a while it said that It cannot complete the scan Press Ctrl+D or write root password and use fsck without any option.
then I entered my root password and executed that command. Then it appeared many messages about some files which didn't exist and asked me whether I want to erase them and I press yes.
after erasing many files I could boot my computer but when I want to do something which can be done only under using root password (for example connecting to internet) and when it asks me for root password. I enter it but nothing happens.
vsftpd. apache, php, mysql and many other programs are working very well.

I tried to upgrade my system but results was the same.

I have erased some libraried which relate to root password and so on.
In my network there is a linux repository and I have access to it via gftp.

Any idea?
I would be grad if you help me.
thanks

Mmm, well it seems you have some strange issue. Try to save what you can with some live-cd and install a true Linux distro like Slackware, you'll understand what i mean with true.

I second to Linux.tar.gz.
And do not use Reiser or XFS without an UPS.

What is UPS?

I am pretty sure it is "Uninterrupted Power Supply". APC does best ones.

Can you log in as root? If not, you may need to boot up to the rescue mode of your installation disk, ( or use a live distro like knoppix ) in order to edit the /etc/passwd or /etc/shadow file to reset the root password. Then boot up again and use the 'passwd' command to change to a new password.

Hopefully, you haven't deleted libraries needed by the PAM system. You might need to use the verify option of the "rpm" command to determine if you need to reinstall some packages. See the "man rpm" or "info rpm" pages for information on this.

If the box can still boot then single user mode can be used to reset root password in a civilized manner. Hopefully FC can be booted in single user mode?

I can log as root in terminal but when I want to open a program in terminal as the root I don't succed to open it.

Do anyone recommend me reinstall FC4 or it is better to wait for a while to find the solution?

Better would be giving more detailed info. Then folks here may be able to help you.
So, you can log in as root from console. What's the error message when executing fails?

You can also check /var/log/message or /var/log/syslog.