How to rename a hard drive? I tried to rename the hard drive of my Macbook from "Macintosh HD" to something else without the freaking space. However, after renaming it, many of my applications showed errors immediately and I stupidly restarted my computer. 

Right now, I cannot log in to my user account because of an error. Everything is blocked.

If someone can tell me how to change the harddrive name back without logging into my previous account?
It seems you have another system - in that you are able to post the question. If it is a mac, you can start the problem system in Target Disk Mode (if it has FireWire), connect it to the working system with a firewire cable and you should be able to change the name remotely.
If you can start in single-user mode (s) that may allow you to bypass the problem.
If you start in verbose-mode, (same link as above), you may be able to see the problem.
If you can start from the Lion recovery disk, or a DVD, that will also allow you to change the drive name.
Finally, if you do get the system restarted, I urge you to check it through Disk Utility (applications > utilities).


I hope this helps.