This is where a simple utility to repair the cache would have been much more useful than a troubleshooter.
Eraser (like the majority of Windows programs these days) uses the Windows installer. The problem you are having is actually with the installer (= part of Windows) rather than the Eraser code or package as such; I think that Microsoft gets its lawyers to vet every error message, to ensure that blame is shifted wherever possible. This is why installation errors can be so difficult to deal with; we are dealing remotely with someone's Windows setup rather than with Eraser (which by now we know something about
).
The reason why this is occurring is, to put it bluntly, that you have not managed to remove all the artefacts of the original, failed Eraser installation from your system. If Joel is right, and the installation cache is the problem, this is a pain, because Microsoft specifically recommends against deleting the cache file, and I don't know enough to know whether this is just belt-and-braces caution or a warning against doing real damage to your system. So this is one possible cause on which I cannot help further.
Just to be sure, we go back to the elements of the brute force removal. You found nothing in the Registry. Can we take it that there are similarly no Eraser folders in either C:\Program Files\ or (if you have it) in C:\Program Files (x86)\ ? Have you by any chance run a Registry checker/cleaner (Joel hates them, but they have their uses at times such as this) to see whether there are still any Eraser related entries you can delete. Reasonable free checkers (which I have had no trouble with) are in CCleaner (not the cleaner itself, but one of the tools embedded it it) and also the Tweaknow Power Pack. In my experience, different checkers identify different items.
Beyond all that, I'm afraid I'm out of ideas.
David