I have ubuntu 8.04 and ubuntu 10.04 on my laptop, and i want to reclaim all the ubuntu 8 space so that i have just one operating system on my laptop. how can i do it? the output of sudo fdisk -l is as follows:

sudo fdisk -l

Disk /dev/sda: 160.0 GB, 160041885696 bytes
255 heads, 63 sectors/track, 19457 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x31a431a3

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1        4959    39833136   83  Linux
/dev/sda2            4960        5233     2200905   82  Linux swap / Solaris
/dev/sda3            5234       12852    61192552   83  Linux
/dev/sda4           12852       19458    53062657    5  Extended
/dev/sda5           12852       19182    50847744   83  Linux
/dev/sda6           19182       19458     2213888   82  Linux swap / Solaris

i dont know which of sda1, ..., sda 6 etc ubuntu 8 is on. how can i find that out?

The actual task is that i think a lot of space is devoted to ubuntu 8, if there is no easy way to get rid of it, then i want to repartition the disk so that about 50 GB of hard disk space is given to ubuntu 10's home folder from the ubuntu 8's home folder. but i hope that there is an easy way to get rid of ubuntu 8 alrogether and just have ubuntu 10 on my system.