Problem with minecraft and allocated ram?

I can load any of my worlds, and i think its because i don't have enough allocated ram. So i change the java arguments to various amounts ( i have 8gbs of ram on my PC) when i did this there was a java virtual machine error, so i went to control panel>system>advanced system settings >environmental variables> new then i try adding the _JAVA_OPTIONS with -xmx(various values) but no value i set fixes the java error, and at this point i cant even start the game even with the default ram allocated

Read more: Problem with minecraft and allocated ram?