I'm trying to dedicate the remaining free space on my hard drive to the /usr directory. I used Knoppix and succesfully formatted it with a ext3 fs and labelled it as /usr. However, when logging back into the Fedora Core 3, the remaining free space for the /usr size was still the same, so I figured I have to edit fstab before any changes would occur. I inserted the line "LABEL=/usr /usr ext3 defaults 1 2". The problem comes when I reboot after that said change because while booting fedora, my comp freezes, with several details reporting the red FAILED instead of OKs now. Also most of the text except for the FAILED and OKs is invisible/missing. Any clue on how to get this working? I can delete the partition with Knoppix again, which will fix the booting problem, but I still want to use the remaining free space for something.

To use a label=xxx in the fstab file you need to create a partition volume label using the tune2fs or label2fs commands. BTW you can always use the partition ID instead i.e.
/dev/hdxy /usr etc...
Where x=drive and y=partition

I've done that before too, and it still doesn't let me boot.

How did you copy the files to the new partition?
Can you post any error messages?