I have make 3 partitions in my hdd the (hda7 where all files of the system are), the hda8 and hda9. The hda7 works fine but in the hda8 and hda9 I have problem. When I try to open the partitions the system give's me a message mount: dev/hda8 is not a block device. I use cfdisk and recreate this two partitions but i steel have the problem. I use slackware.I don't have but blocks in my disk!!!Disk file system is ext3 in all partitions!

Thanks for your help!!!
Free software!!!

What command are you using to open the devices? As far as I remember should be...

mount /dev/hda8 /mount/nameofshortcuttohddevice

your gonna have to make a link somewhere so I'll give an example...

$ su
# mkdir /mount/hda8
# mount /dev/hda8 /mount/hda8

that is the basic way, if you want it to boot up during boot time your gonna have to edit fstab (/etc/fstab) but ask me if you want to know how to work with that file and I'll spend time with you on that, first try the above to see if that is what your problem is.

Post the output of the command
fdisk -l (small L and command needs to run via root)

What is the exact command you are using to mount the filesystem?

This is the problem i can't make mount i use this mount/dev/hda8 and i take the message mount: /dev/hda8.From KDE the same problem.
This is the fstab you ask
/dev/hda10 swap swap defaults 0 0
/dev/hda7 / ext3 defaults 1 1
/dev/hda8 /dev/hda8 ext3 defaults 1 2
/dev/hda8 /dev/hda8 ext3 defaults 1 2
/dev/scd0 /mnt/cdrom auto noauto,owner,ro 0 0
/dev/hdd /mnt/cdrom1 auto noauto,owner,ro 0 0
/dev/fd0 /mnt/floppy auto noauto,owner 0 0
devpts /dev/pts devpts gid=5,mode=620 0 0
proc /proc proc defaults 0 0

Did you format the partitions? To format hda8 with an ext3 filesystem:
mke2fs -j /dev/hda8

/dev/hda8 is not a valid mount point. You need to create a directory to use as mount point as posted above. Example:
mkdir /mnt/hda8

I asked for the output of fdisk which would verify the partitions actually exist.