It seems you have not really understood what
Originally Posted by dudeman41465
If you can, I would use some other LiveCD to actually recover your personal files and move them to a backup device prior to mucking about with your OS.
After that, I would go with John's suggestion and install the latest version of your OS.
Originally Posted by John VV
You gave VERY little information so only a wild guess can be given
if a gui is being used then the /tmp/.X0-lock might need removing
Also centos 5.5 is unsupported you NEED to upgrade to the ONLY supported 5 version
you are two versions out of date .
had mentioned. Well the simple steps to do, if you need to back up your data, please, find a LiveCD such as Ubuntu, Fedora, CentOS etc., boot with that CD. Once when you get into to the option "Try Ubuntu ... Fedora ... CentOS" based on the distro live cd you use, get to the GUI. Thereafter, just copy the files from the HDD that has your problematic CentOS, to another medium, either a HDD or a USB drive, based on your data size.
Try this and you'll really appreciate yourself for the effort.
Best of luck.