Installer trying to open following manual extraction

So, I’ve been running into what I thought were timeout issues (500 errors). My host’s tech support pointed me in the direction of PHP configurations that… didn’t quite fix everything, but seemed to solve the timeout problem. Instead of getting the 500 server error message, from that point on I consistently got what I think was a 200 error (I could be remembering that incorrectly, though). I “Tried Again” quite a few times with no luck. Most of the files were unpacked, but things were just not cooperating. The site had no front-end; I got the wp-admin login page to show up, but that was the extent of the WordPress setup that successfully deployed, apparently.

Not knowing what else to do, I tried a manual extraction. I copied the contents of the ZIP file to the directory where I put said ZIP file and the installer. Now, though, when I try to run the installer my browser tries to open it. I have permissions on the file set to 777, but I cannot touch it with a web browser, other than it trying to download the file or open it with an external program.

Thoughts?