recently i install debian 5.0 on my laptop. the partition table as below:
partition 1 - vista - ntfs (P)
partitoin 2 - data - data (P)
partition 3 - linux ext2 (L)
partitoin 4 - swap

after installing, i discover my partition 2 got hidden and no way to unhide it. why it hide it in the first place?

Please define "hide". What, exactly, are you trying to do? What have you done? What are the symptoms of the problem?

Also, post the output of "fdisk -l" and "mount"

And the contents of the file /etc/fstab would be usefull too.

Sorry that i wasn't clear in the first place.
The system id of the partition 2 become 17 (hiddent-NTFS) instead of the 07.

This is the rough idea of my fdisk partition output:
Device Boot Id System
/dev/sda1 * 7 HPFS/NTFS
/dev/sda2 17 hidden-HPFS/NTFS
/dev/sda3 f W95 Ext'd (LBA)
/dev/sda4 83 Linux
/dev/sda5 linux swap

I could not change the /dev/sda2 to 7 instead. I tried with fdisk linux and it changed back to 17 after reboot. And I tried with disk magment vista, it seems like the partition is greyed out. i am wondering what could have gone wrong.

Sorry that i could not provide further detail on fstab, ( i remember there is no ntfs partitions being mounted when i booted into it ) as i have wiped the partition in the effort of recovering the data in /dev/sda2 ...

I would like to give it another try, but i don't want it to end up in the same situation again...

thanks.