Could not download all repository indexes

Ho installato ubuntu6.1 su un portatile toshiba satellite l10-125, 256 mega di ram CPU Celeron M370, 64 mega di ram su scheda integrataIntel 852GM,HD da 40 giga.

E' la versione più adatta ad una macchina del genere?

Ora la domanda:
Ho installato la versione alternate(per pc con poca Ram) ma nonostante navigo in internet, gli aggiornamenti non li fa fare. da la scritta :Could not download all repository indexes.

Ho cercato di leggere le risposte precedenti, ma non sono riuscito a eseguirele istruzioni.

questo è il mio file sources.list:

#
# deb cdrom:[Ubuntu 6.10 _Edgy Eft_ - Release i386 (20061025.1)]/ edgy main restricted

deb cdrom:[Ubuntu 6.10 _Edgy Eft_ - Release i386 (20061025.1)]/ edgy main restricted

deb http://it.archive.ubuntu.com/ubuntu/ edgy main restricted universe multiverse
deb-src http://it.archive.ubuntu.com/ubuntu/ edgy main restricted universe multiverse

## Major bug fix updates produced after the final release of the
## distribution.
deb http://it.archive.ubuntu.com/ubuntu/ edgy-updates main restricted universe multiverse
deb-src http://it.archive.ubuntu.com/ubuntu/ edgy-updates main restricted universe multiverse

## Uncomment the following two lines to add software from the 'universe'
## repository.
## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team, and may not be under a free licence. Please satisfy yourself as to
## your rights to use the software. Also, please note that software in
## universe WILL NOT receive any review or updates from the Ubuntu security
## team.
# deb http://it.archive.ubuntu.com/ubuntu/ edgy universe
# deb-src http://it.archive.ubuntu.com/ubuntu/ edgy universe

## Uncomment the following two lines to add software from the 'backports'
## repository.
## N.B. software from this repository may not have been tested as
## extensively as that contained in the main release, although it includes
## newer versions of some applications which may provide useful features.
## Also, please note that software in backports WILL NOT receive any review
## or updates from the Ubuntu security team.
# deb http://it.archive.ubuntu.com/ubuntu/ edgy-backports main restricted universe multiverse
# deb-src http://it.archive.ubuntu.com/ubuntu/ edgy-backports main restricted universe multiverse

deb http://security.ubuntu.com/ubuntu edgy-security main restricted universe multiverse
deb-src http://security.ubuntu.com/ubuntu edgy-security main restricted universe multiverse
# deb http://security.ubuntu.com/ubuntu edgy-security universe
# deb-src http://security.ubuntu.com/ubuntu edgy-security universe

Grazie per l'aiuto