You can try to download it to your machine, and run from windows as D:\wubi.exe
You can't install Wubi from an alternate ISO. For 12.04.2, if you want to install from a 32bit desktop ISO, you can save it in the same folder as wubi.exe before running (both available from http://releases.ubuntu.com/12.04
This wubi.exe can also install standalone (no ISO).
To install from the 64bit desktop ISO (not alternate), there is a bug which has been patched, but not released so you'll need to use the wubi.exe from here: http://people.canonical.com/~evand/w...273-signed.exe Save that in the same folder as the desktop-amd64 ISO before running. link