When LightTable is installed in Program Files under Windows 7 (which protects anything in Program Files from being modified by non-admin users), its upgrade fails, with the following errors in the console:

Error: EPERM, open 'C:\Program Files\LightTable\tmp.tar.gz'
Error: ENOENT, open 'C:\Program Files\LightTable\tmp.tar.gz'
Error: EPERM, mkdir 'C:\Program Files\LightTable\tmp'

The tmp folder should probably be placed in %APPDATA% rather than in LightTable's installation folder. There may still be problems with admin permissions later — I haven't looked into the upgrade code to see whether it needs to replace any files in LightTable's own installation directory (which would also be protected by Windows 7), but at least the upgrade would be downloadable.

A good first step, though, would be to mention this problem in the documentation. Perhaps we could suggest that users install LightTable in their home directory somewhere? Or say "If you're on Windows 7 and having problems upgrading, move your LightTable folder out of Program Files, run the upgrade, then move it back into Program Files". (Another option, which I do NOT recommend, would be to tell users "just run LightTable with Adminstrator permissions when you need to upgrade" — but that would make them vulnerable to malicious plugins. Which may not exist yet, but someday someone would create one. Best to head off that problem at the pass.)

Note: I have not tested this on Windows 8 (nor on the Windows 10 developer preview), but I wouldn't be surprised if the same problem exists there — if those versions protect Program Files, then they'd have the same problem.