toshiba portege m100 stopped upgrading from ubuntu 12. to 13.

I have a toshiba portege m100 that I couldn't locate a recovery disk for, so I installed the ubuntu 12.3, and it was working fine. Then, I got a message to upgrade to the 13.04 version, and as it was going thru the process, it stopped and I got a message that it couldn't continue the upgrade. Now, when I log into the the OS, my computer will not boot up to let me go online. What should I do, to reinstall the old 12.3 version? When I tried to reinstall the OS with the disk, it doesn't recognize the disk in the drive. Please help me...thnx much.



1) Firstly it was 12.04 which was a LTS (Long Term Support) version. Normally releases are April (O4) and October (10).

2) Reinstall 12.04 IF YOU WANT TO.

3) An alternative is to use a lighter version of 13.10 e.g. Lubuntu or Xubuntu