What makes you think the download is 32-bit Ubuntu?

Phil pointed you to a page with bittorrents. I find that is the fastest and most
reliable way to get Ubuntu. The one to select is: ubuntu-12.04-desktop-amd64.iso

Then you feed the torrent into a bittorrent download program such as
Transmission. Just double-clicking on the file should automatically start
Transmission. Highlight the file and select "add".