ID:2808704
 
I will describe the sequence of my actions:
1) Installed Byond.
2) Launched it.
Result: it closed after 2-5 seconds of loading.

I hope for someone's help.
After starting BYOND, in your system tray (up arrow next to the system clock on your task bar), is there a BYOND icon that you can right click and hit "Open" on? For me, sometimes BYOND hides itself there instead of opening fully.
No, there is no icon
First I would try turning your PC off and back on. I'm obligated to suggest this.

If you're still having issues then I would uninstall BYOND, temporarily disable your antivirus (or add BYOND to your exclusions), then re-install BYOND.
Already done all of these steps, not working...