Hi everyone, I've got a big problem: I've erased by mistake an important library (gclib or something like that) and this library was at the base of couple of programs: the result is that the OS now doesn't boot. My question is: is it possible to reinstall the OS without modifying the current settings and archive files? I ask this because there is a similar "trick" in Windows, in which, thanks to the setup CD, you can reinstall the OS overwriting just the files of the OS, without touching the others.

Thanks a lot for your answers, I'm going crazy!!! (and sorry if the forum isn't the right one)

How is it possible? I'm not here to blame you, we learn from our mistakes, so learn that under GNU/linux, you've got a packages manager that handles softwares and libraries updates, installing and removing... The one for fedora is yum, and a GUI for it is yumex. By using yum, you won't removing a base library by mistakes, updates for every packages on your system will be automatically updated, it will deal with dependencies when installing new softwares...
By the way, I'm not sure but I think that your fedora media surely have live-CD mode, or better a recovery mode, thus you'll be able boot a system.
The idea is:
-mount your hard drive which contents "/lib" (assuming you've removed the libc)
-copy by hand the libc used by the live-CD into mounted "/lib"
-reboot on your system, hope that works
-take a look to yum to re-install properly libc with yum.
If the fedora media have a recovery-mode, maybe this kind of problem can be handle automatically...
Good luck.

You should use a Live-CD or Live-DVD to launch a Linux system on your PC. Then you have to chroot into your harddisk-based system and re-install glibc. Use the force option to install glibc, if you are using RPM or something based on that, that way existing files from the glibc package will be overwritten - otherwise you will get a message that glibc package is already installed.

Doing it this way you can keep all your settings and data files intact.

Thank you both, I've tried the solution of jf.argentino, but now, at the boot, the message is : kernell panic - not syncing: Attempted to kill init!
What's the next step?