Whether your windows installation is 32-bit or 64-bit does not matter for Ubuntu since it's not dependent on windows. Do not get confused by the amd
word in amd64
, it's just a marketing name that refers to the same architecture: 64-bit (well, I may not be fully technically correct here, but you can expect an amd64
Ubuntu image to run on Intel machines). i386
is used for 32-bit stuff. If Wubi detects that you've a 64-bit capable processor, it downloads the 64-bit version.
If you really want to force the installation of a 32-bit image, see How do I force Wubi to download and install 32 bit version?