Okey, Sio I kicked out all Windblows stuff, and I'm running Slackware 9.1 only.
I'm running two harddrives, one 80 gig and one 160 gig.
I installed Slack on the 80 gig, and at that time, my 160 gig was NTFS, since I was in need of some files there.
I mounted the Win drive, got my files, and then deleted the partitions.
Then I created four Linux partitions of 40 gigs, which I wanna use.
I then did this in my fstab:
/dev/hdc2 / ext3 defaults 1 1
/dev/hdd1 /mnt/hdd1 ext3 defaults 1 1
/dev/hdd2 /mnt/hdd2 ext3 defaults 1 1
/dev/hdd3 /mnt/hdd3 ext3 defaults 1 1
/dev/hdd4 /mnt/hdd4 ex3 defaults 1 1

And some floppy and cdrom stuff, which I guess isn't all that important.

However, it would appear that Linux is not able to use that extra space.
I can't mount it, then I get the usual error message, unknown FS or too many mounted devices.
I also tried actually using the space, copying my movies over to /mnt/hdd1 which did not work, got an error message because I lacked space, and I can assure you, there was enough space.

I tired searching around a bit, but I never found any help about this exact problem, or anything that was close.

Are you sure the 160G drive is mounted on hdc or hdd? Isn´t it hdb?
Try to mount in manually doing:
mount /dev/hdb1 /mnt/someplace

I double checked, and did an fdisk -l and found that it is hdd, I'm 110% sure.
And mount /dev/hdb1 /mnt/hdd1 says "unknow device"

Post the whole fstab here.

Verify the drive is really hdd.

Did you format the new partitions?
For ext3:
mke2fs -j /dev/hdxy (where x = drive location, y = partition ID)

Okey, this is the exact fstab:

/dev/hdc2 / ext3 defaults 1 1
/dev/hdd1 /mnt/hdd1 ext3 defaults 1 1
/dev/hdd2 /mnt/hdd2 ext3 defaults 1 1
/dev/hdd3 /mnt/hdd3 ext3 defaults 1 1
/dev/hdd4 /mnt/hdd4 ex3 defaults 1 1
/dev/cdrom /mnt/cdrom iso9660 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

Boy do I feel stupid, I didn't know about that command, it's formatting now, so that was probably the problem. Thanks a lot!!

There´s no hda on your fstab?

No? Is that wrong?

did you create the directories ?
/mnt/hdd1 - /mnt/hdd4. if they don't exist, it can't mount.
fdisk -l will list all your partitions also.

It's okey now, it's working =)

my fault. i didn't catch the formatting command above where you said it was working.