I need to know where is my ubuntu partition

In terminal (ctrl+alt+t) type:

sudo fdisk -l

The partition that says "Linux" under the "System" column will be the partition that Ubuntu is on. It will have a label such as
'/dev/sda1'. I really like an application called "gparted". It is a very uselful tool that makes it easy to manage your partitions. If you want to install it open a terminal and type:

sudo apt-get install gparted

Then find it in the dash or app menu. gparted will make it a lot easier for you to see your filesystems, it has everything nicely labeled and coloured in a graph. You can also use it to shrink, grow, move and remove partitions and more. Hope that helps.

Thanks for help..Great application...I have these: /dev/sda1,2,3,5,6 and anallocated. the first 1 is nfts system reserved 100 Mib, 2 ntfs( here think window7 is at)255.95GiB, 3 extended with 209 Gib but nothing used, 5 ext4 with 206Gib I believe ubuntu is here. is the one sharing the graphic more space with 255 ntfs...can I just delete and gain some space.??And my hard disk is 500GB. thanks.

What do you mean by sharing the graphic? You can delete partitions to gain space, but you must allocate that unused space to one or more of your other partitions. Do not delete the partitions containing Ubuntu and Windows (obviously), or partition labeled *Swap* or *Boot*. Also you are correct that the NTFS is Windows, (ntfs and fat32 are used by Windows), and Ubuntu is the ext4 (Linux uses ext2, ext3, and ext4, but ext4 is now the default).

thanks for answering, Id like to send you the screenshot but I dont know how to do it here. The graphic is rectangular square showing me how the disk is used.
let me give a better idea: /dev/sda1-ntfs 100MiB, /dev/sda2-ntfs 255GiB these are for microsoft and specific functions as you say. /dev/sda3- it says: allocated and inside has /dev/sda5 -ext4( heres Ubuntu!!!!! :) )but theres also something else: unallocated -3.24GiB.
at the end theres another Unallocated -1.02GiB.

I discovered with your help where ubuntu is but now I want to get rid of this unallocated spaces and yield the space to ubuntu. thanks

any help??

If you want to send screenshot use Imageshack or similar service.Upload your screenshot there and put here a link.If you just installed Ubuntu (meaning there is no valuable data) I suggest you reinstall.I believe you see rectangle because that partition is in use and you can not manipulate with it.You have Gparted on your Ubuntu live CD.Use it in live session to delete existing non-Windows partitions.Maybe just delete partitions inside of extended partition.I will format like this:

1. 10-15GB to root mountpoint /
2. 2GB swap
3.rest of free space mountpoint /home

You can put swp as last partition.This way you will have separate home partition,meaning in case of reinstall,upgrade... your files will be safe.

thanks for helping heres the image

http://yfrog.com/0jscreenshotfrom201304151p

[URL=http://img14.imageshack.us/i/screenshotfrom201304151.png/][IMG]http://img14.imageshack.us/img14/4492/screenshotfrom201304151.png[/IMG][/URL]

Ubuntu is on sda5 and that partition is over 206GB.I will delete that partition and resize extended partition in a way not to have unallocated space.Then you can reinstall ubuntu and during installation process you can make partitions.Other way is to first make partitions with Gparted and during installation just select where goes root,home and swap.Like I told you I will do it this way:

1. 10-15GB to root mountpoint /
 2. 2GB swap
 3.rest of free space to home mountpoint /home