My minecraft server won't work I need technical help?

it keeps saying "Error occurred during initialization of VM. Could not reserve enough space for object heap. Error: Could not create Java Virtual Machine. Error: A fatal exception has occurred. Program will exit."
i'm using the basic vanilla server thats provided from the minecraft website. In the past it ran perfectly fine a few days ago but now im not sure what has happened or how to fix it.
my laptop is running on 64 bit windows 8.1 with 4gb ram and i setup up my server with 2gbs.
i'm also using java 7 if that helps.

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