[Mongoose]

Yeah, from the standpoint of a normal end-user, #2 seems like the best option, all things considered.  #1 isn't really practical, since there are a number of mods that take advantage of 7Zip's superior compression abilities, and #3 potentially raises bandwidth/HD space/fragmentation issues.  I doubt anyone who's relying on the installer is going to mind, or even notice, a bit of extra delay.

(One has to wonder why the 7Zip format is so ass-backwards in the first place, though...)

[Goober5000]

And; is it possible to download just the last part of a file first and then read it?  I know download managers can resume files, so why not get the file size, download the last xx bytes (I don't really know if this is feasible, so please forgive me if it's out of the question), and read the TOC?

This is actually what the 7Zip guy and I are discussing now.  I'm going to try some things this weekend.

I feel your pain. Just slap a "Verifying contents of package..." progress indicator on it and let it take as long as it likes.

Win.

[Tomo]

"Verifying..." blah is how Windows Installer (MSI etc) starts anyway.

It shows the endless progress bar, for that, so if you've got some indication from the API of how much work there is to be done, and can show a real progress bar then you are doing it so much better than Microsoft.