Win XP, SP3, did the download. Not using Avast to monitor realtime web traffic. Monitoring software that checks downloaded files for malware, MS Sec. Essentials, did not flag the download as a questionable file. Presumably Avast does not either or others would have noted that.
With the other modules activated except for realtime web traffic monitoring, the sandbox popped.
On scrolling options, run in Sandbox worked fine. On cancel the install, got a Win XP OS error popup message, "Windows cannot access the specified device, path, or file. You may not have the appropriate permissions to access the item."
I have administrator privilege. Did the error message mean the Auto Sandbox, on the "kill it" selection, did not fully kill it?
If so, that might be a serious bug. Run in Sandbox, okay; but choose to kill, and it tries an install anyway? Have any other users, on other systems tried that option?