I've got a ubuntu 11.10 which has lost its support in May 2013, now I'd like to reintall up to the most up-to-date LTS, which is 12.04. My question is regarding my current partitions and doing backups. Is there a safe way to backup my data on some local partitions instead of copying files into DVDs/external drives (this is very uncormortable in my situation). Following are system commands shoing my disk:

$ lsblk
NAME   MAJ:MIN RM   SIZE RO MOUNTPOINT
sda      8:0    0 232,9G  0 
+-sda1   8:1    0  48,8G  0 
+-sda2   8:2    0    63G  0 
+-sda3   8:3    0     1K  0 
+-sda4   8:4    0  53,7G  0 /
+-sda5   8:5    0  18,6G  0 
+-sda6   8:6    0  25,5G  0 
+-sda7   8:7    0  23,3G  0 [SWAP]
sr0     11:0    1  1024M  0

and

$ sudo fdisk -l
[sudo] password for xyz: 

Disk /dev/sda: 250.1 GB, 250059350016 bytes
glowic: 255, sektorów/sciezke: 63, cylindrów: 30401, w sumie sektorów: 488397168
Jednostka = sektorów, czyli 1 * 512 = 512 bajtów
Rozmiar sektora (logiczny/fizyczny) w bajtach: 512 / 512
Rozmiar we/wy (minimalny/optymalny) w bajtach: 512 / 512
Identyfikator dysku: 0xc3ffc3ff

Device    Boot  Beginning   End          Blocks     ID  System
/dev/sda1   *        2048   102402047    51200000    7  HPFS/NTFS/exFAT
/dev/sda2       215044096   347080703    66018304    7  HPFS/NTFS/exFAT
/dev/sda3       347082750   488392064    70654657+   5  Extended
/dev/sda4       102402048   215042047    56320000   83  Linux
/dev/sda5       395905923   434975939    19535008+  83  Linux
/dev/sda6       434976003   488392064    26708031   83  Linux
/dev/sda7       347082752   395905023    24411136   82  Linux swap / Solaris

In the beginning I had Windows Vista pre-installed with the machine when it was bought (damn!) and I installed linux (the one I have now). The windows-program in master boot record has been overriden by grub and now I can boot with both Windows and Linux.

This is list of mounted devices:

$ mount
/dev/sda4 on / type ext4 (rw,errors=remount-ro,commit=0)
proc on /proc type proc (rw,noexec,nosuid,nodev)
sysfs on /sys type sysfs (rw,noexec,nosuid,nodev)
fusectl on /sys/fs/fuse/connections type fusectl (rw)
none on /sys/kernel/debug type debugfs (rw)
none on /sys/kernel/security type securityfs (rw)
udev on /dev type devtmpfs (rw,mode=0755)
devpts on /dev/pts type devpts (rw,noexec,nosuid,gid=5,mode=0620)
tmpfs on /run type tmpfs (rw,noexec,nosuid,size=10%,mode=0755)
none on /run/lock type tmpfs (rw,noexec,nosuid,nodev,size=5242880)
none on /run/shm type tmpfs (rw,nosuid,nodev)
binfmt_misc on /proc/sys/fs/binfmt_misc type binfmt_misc (rw,noexec,nosuid,nodev)
gvfs-fuse-daemon on /home/tomasz/.gvfs type fuse.gvfs-fuse-daemon (rw,nosuid,nodev,user=tomasz)

It's strange (I don't remember such thing) that my current linux uses only one partition (/dev/sda4). But, anyway, it seems like that.

My final question is: am I able to use one of the existing linux partitions for a backup and install ubuntu 12.04 without removing neither windows nor ubuntu 11.04? I mean - will grub automatically accept both old windows vista and 2 linuxes (old 11.10 and "new" 12.04)? Is there any hidden operation done while installation that could harm my custom-backup-partition while installing?

my fstab file:

proc            /proc           proc    nodev,noexec,nosuid 0       0
# / was on /dev/sda4 during installation
UUID=d44e89f5-9da2-48eb-83b3-887652ec95d2 /               ext4    errors=remount-ro 0       1
# swap was on /dev/sda7 during installation
UUID=bbe50535-ba57-434a-9272-211d859f0e00 none            swap    sw              0       0

sda5 and sda6 are trash partitions created during unsuccessful linux installation (this was linux installation before my current installation), I didn't delete these partitions, but I have access to them (and I can use them as backup partitions).

edit: second question is: why does lsblk show /dev/sda having 232,9G while fdisk shows that it has 250.1GB? Where does the difference come from?