Corrupted file Ubuntu OS download (11.10 & 12.4)

Solution 1:

How did you download the files. Is it normal http/ftp or Torrent download. Http and ftp downloads are too much prone to file corruption. I would suggest you to download the files using Torrent protocol, which has in-build feature to check the correctness of the download. If you have downloaded the file using Torrent then also check the ISO MD5 checksum with the Ubuntu website MD5 checksum. If both are same then there is no problem with the ISO file.

Secondly, are you using a CD or Pendrive to install the Ubuntu? In case of CD, I have seen such issues if the CD has scratched. Try the pendrive install.

Solution 2:

Personally I download from a bittorrent client and FORCE a recheck once it's complete to make sure the iso image is ok, then I burn at the slowest speed possible onto a good quality DVD using Brasero or ImgBurn for Windows and both tend to work fine...