Infected by trojan without executing its host file?

So here's the story.  Tonight i got my first virus since running windows 98. I downloaded what i thought was a movie file, but when i extracted the zip file it was packaged in i noticed the main file was a exe file instead of a video file.

 

I went to delete it.

My incorrect assumption though was that i was safe because i did not run the exe file. my computer immediately started going wonky (unable to open programs or folders, and I heard the hard drive active) so i physically cut power to my machine in a panic.  When I restarted norton detected a trojan that originated from that very exe file i never executed.

 

So my question is, did the thing execute itself?  How did it infect my system without the file i downloaded being run?

 

Thanks in advance for any help.