Ok, thanks for your interest in the first place.
I bought a second hard drive, (seagate, 1TB) and followed some instructions about how should i format it. Unfortunately i don't remember where. I ended up with a fully functional disk and copied to it about 400 Gb of data. As far as i knew there was a single 935Gb partition. I needed to shrink the partition to create a smaller one i need in vfat, and every partition manager i tried (gparted, parted, Kde's partition manager, testdisk) sees the disk fine, as a 1TB unallocated space hard drive. I realize, the data was copied directly to /dev/sdb, not /dev/sdb1. I can access the data with no trouble, it gets mounted on boot and on use i have no issue. But i can't edit the partition table, because as far as parted is concerned, it's all unallocated space. I tried running testdisk (even deep) and parted rescue, but they don't see any partitions. Any thoughts? maybe some way of making a new partition table without erasing data=?

Thanks in advance

What dark magic are you performing?

Post your /etc/fstab, the output of "mount" when the data drive is mounted, and the output of "fdisk -l".

mount's entry:

/dev/sdb on /media/data type ext4 (rw)

everything else on mount is about the other hard drive.

annd the fdisk -l:

Disco /dev/sdb: 1000.2 GB, 1000204886016 bytes
255 heads, 63 sectors/track, 121601 cylinders
Units = cilindros of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x3d8bf86f

Disposit. Inicio Comienzo Fin Bloques Id Sistema
[evildrake@chakra ~]$

It is in spanish, but still, there's no partition shown. Still, with the partition mounted, i can access the data perfectly.

You didn't partition the disk.
So it has no partitions, so there's no partition table.
There is a filesystem, but that's all there is.
You did not do it "right", even if it is "working".

You need to save the data somewhere else, partition the 1TB disk, format it, and then copy the data back.
Then the partitioning tools will work as expected.

Yeah, i understand that much. The thing is, moving 400Gb around is impossible for me atm, so i was wondering if there is a way around, to partition it but stay able to rescue the information.

Not AFAIK.

Well, bummer. Thanks for your help, though.

I also can't help, but interested in what sector zero looks like (the filesystem metadata). Want to post the output from this (merely reading that sector)?.

Here's the output.

Are you booting off that disk ?.
Didn't expect to see that in the MBR - no reason why not I guess.

Soooo ...
I see a blank partition table. I'd reckon you could allocate a partition to cover the data you have.
Not recommending it for you if you can't back up your data, but I might have to go find an old disk to test this.

O.K., ignore the above. Your data will be at risk.

I had an old 4 Gig drive sitting around. Zeroed it, and formatted as ext3, copied some data over.
Made sure that was accessable, then added a partition to cover the entire drive. Can't mount it. Non-zero data starts at sector 2, not 63 as would normally be needed for a "standard" partition.
I played with the start sector of a partition covering the entire drive, but couldn't get it to mount.

Well, you sir are too kind. Now i know for sure that the only way i can partition my drive will erase all the data, so a full backup is in order. Thanks for your commitment.

Not entirely philanthropic on my behalf.
This interested me enough to go have a look.

Backups (current ones) are always an excellent idea.