از اینجا توضیحات رو بخون توی خود گوگل هم سرچ کنی هست. از اینجا
http://releases.ubuntu.com/precise/فقط ایزو رو بگیر که رایت کنی روی سی دی. 32 یا 64 بیتی رو رعایت کن.
Alternate install CD
The alternate install CD allows you to perform certain specialist installations of Ubuntu. It provides for the following situations:
setting up automated deployments;
upgrading from older installations without network access;
LVM and/or RAID partitioning;
installs on systems with less than about 384MiB of RAM (although note that low-memory systems may not be able to run a full desktop environment reasonably).