Hey bone-bags

[Loretta]

Windows 8 Is a bit of a jerk when it comes to older files, such as a v83 server. They tend not to get along.
The Maplekey Client does not need to overwrite the actual "MapleStory" Client, they coexist with each other. You just don't use the Maplestory one.

Maplekey, just like many other servers, is seen as a virus in a lot of systems. However, it is not. More than likely, it's any anti-virus or firewall you may have on. Try disabling both and re-extracting.
The maplekey client MUST stay in the folder for it to be used, however, a shortcut can be made from that folder. In order to run the game, you need to run it as Administrator (Right click, run as admin).

Let me know if the anti-virus and firewall turn off works!