Need some help with registry

Hello,

I recently found PortalApps and I'd some idea about making one of my game portable, Vindictus.
But I've the following problem : the game won't run until a key is missing in the registry and this key is located in HKEY_LOCAL_MACHINE.
Since I want to use the game on my school computers, I don't have privileges to add this key with a simple .reg file. So I'm asking you if there is a way to bypass the privileges? or simply change the folder of the key to HKEY_CURRENT_USER by modifying a file or maybe use the key in a .ini file?

Here is the key I've to add:
[HKEY_LOCAL_MACHINE\SOFTWARE\Nexon\Vindictus\en-US]
"Executable"="E:\\Vindictus\\App\\en-US\\Vindictus.exe"

This is the only key needed and the game should run, thanks in advance!