How big is your hard drive? Your disk may not be full, but that particular partition may be. Did you create a /home partition? Or just a / partition? How are you deleting files from it? Can you get a prompt? Have you been downloading files or have you run an update with yum/apt/red-carpet recently? Sometimes you have to eliminate more than just a few files before it will be alright again.
 
If you can't get to a prompt to check and/or delete info off of that partition you may have use a rescue or a live cd rescue. 9.1 comes with rescue on cd 1. Just put the first install disk in, and follow the on screen instructions to go into rescue mode. I believe, like with RedHat, you can mount you Hard Drive files by going:
 
mount /mnt/sysimage
 
There should be instructions along the way on how to do it though. I haven't rescued in Mdk for a while so I'm a little fuzzy on how Mdk does it.
 
Are you by chance dual booting with Windows? If you can get a copy of Partition Magic going, you can check how full your Linux partitions are with that.

My hard drive is small (4GB) I have three partitions 1) / (root) 2) swap 3) /home. I've alocated 2,2 GB for / , something about 300MB for swap and the other space for /home. No other system (windows). Last two days I used Mandrake only to programming in C (KEdit for writing) and Rxvt.
 
I can get prompt after about 3 tries of my Linux to get to X.
I'm sure that before yesterday's shuting down of my computer there was at least 300MB free on /. Today - nothing. I'm deleting files with rm. I've just deleted some *zip files which I don't need. I;ve deleted about 30 MB and nothing have happened. Disk is full.
 
Linux says that only / is 100% used. /home is only 13% used

I would be willing to bet that the problem is that your / partitions is really stuffed, and you must remove even more from it to get things going again. I have had this problem on my 6 gig box more than once. I would start uninstalling packages using either
 
rpm -e
for ones you've installed yourself, or uninstall packages with urpmi. You may have to do some drastic slashing before things get freed up again. CAUTION: do not rm folders of apps, otherwise rpm -e will not know how or where to delete those particular packages. Only use rm as a last resort. What DE are you using? Gnome? KDE? a quick fix might be to uninstall Gnome and/or KDE and just use IceWM. That should free up a lot of space. Then you can rebuild.
Another option may be to do a complete re-install, only this time, give even more space to / and take it away from /home. That way, if your /home partition gets too full and you run into this same problem, you can transfer some of your home files to cd or a reader/writer stick and be back in action. Hope this helps you.

I'll try rpm -e
 
but tell me how can I uninstall this way for example GNOME (I'm using KDE).
rpm -e <what?>
and what about dependencies?

I don't think you can get rid of either of those with rpm -e. I believe you'll have to do it via urpmi. I'll have a look on my Mandrake box, find out, and get back with you on this, unless someone else reading this thread can tell us how before I get back to you. In the meantime, if you have any rpms that you installed, and you don't mind un-installing them until you can get enough space to maneuver, I'd be doing that.

I agree with the statement that the disk will not be full, because my / partition is only 200 MB, and just lke spejbl I only using Mdk-9.1 in my box.
 
But spejbl, can you show me the result from command:
 
$ df
 
It will tell us how full is your harddrive.

I've solved the problem. there was 300MB .xsession-errors file in my /root directory I didn't see it before because dot is at the start of it's name. Yesterday I used find / -size +102400k and only one file was bigger (.xsession-errors). I was too lazy to open it so I deleted it and everything is alright now.

Wahoo!!