How to fix “16 bit MS-DOS Subsystem … illegal instruction” installing U1 on Windows XP?

Question

I was trying to install Ubuntu One client on my Windows computer, and got this:

I tried clicking ignore, but then there were even more errors.

Answer 1

This error indicates that a DOS program is being run. Since the Ubuntu One executable for Windows (or its installer) is unlikely to have any legacy DOS components, it seems likely that the installer you downloaded is corrupted.

Just about any download can be corrupted, but the Ubuntu One installer is not very large, so the risk of corruption is usually pretty low. So I visited the download page for the Ubuntu One client for Windows, and downloaded it myself.

I examined the downloaded file (on my Ubuntu system, with file and less), confirming that it did not download correctly. Instead of the executable installer for Ubuntu One, the downloaded file was a web page!

So I renamed the file to have a .html extension, and opened it in a web browser. It looks like it might be a problem with OpenID--that, for some reason, the download page thinks you have to be logged in to download the Ubuntu One client (but downloading it while logged in doesn't work either).

I'll try to look more into this. Ultimately, it should probably be reported as a bug in the Ubuntu One website. Ordinarily we consider bugs off-topic here (reporting them, and most investigation of them), so please don't be alarmed if this question ends up getting closed.

I'm making this answer community-wiki. Anyone with information about this should feel free to edit this answer (unless moderators say not to continue work on this here, of course).

Update

I've reported this as a bug. It is bug 1037771 on Launchpad. I reported it against the ubuntuone-servers project rather than the ubuntu-website project, since the domain is one.ubuntu.com (which I believe is administered separately from the main site). I think I got the project right; if not, a triager or developer should be able to retarget it to the correct project.

I recommend subscribing to the bug (so you receive notifications about it), and indicating you are affected using the green This bug affects... link near the top of the bug page. In addition, I recommend posting your screenshot, as well as any pertinent information that I may have neglected to include, in the bug.

If you don't have a Launchpad account, you'll have to first create one in order to do this. (To do that, click Log In / Register at the upper-right corner of the main page, or any Launchpad page.) But having a second person confirm the bug on Launchpad often substantially shortens the amount of time it takes to fix important bugs like this one. (I say it's important as it is likely to affect a large percentage of users and render the product completely unusable for them; for these reasons, I believe the bug is likely to get swift attention on Launchpad, once it has been formally confirmed.)

Update 2

For the benefit of others finding this question:

The bug has been fixed, and the Ubuntu One client for Windows now downloads correctly.

Anyone who has this problem can simply re-download the installer (the proper file is currently about 20 MB large), and it should be usable.