It should come up with this
Locate the memory part(http://puu.sh/3LhY) Its under the Proccesor.
I saw that my laptop has 8192mb of Ram
If you dont know how much gb that is reffer here:
1GB 1024 2GB 2048 3GB 3072 4GB 4096 5GB 5120 6GB 6144 7GB 7168 8GB 8192
If I wnat 6 GB I have to rember that half the 6144(6gb) is 3072(3gb)
So I open up notepad and the this code:
javaw -Xmx6144m -Xms3072m -jar "C:\Users\Marc\Desktop\Minecraft.exe"
And the 3rd(my name) you put your User name on your pc.
Now you go to the start menu and serch CMD and RUN AS ADMINISTRATOR!!
Then click the top left cmd icon and go to edit>paste(puush dosnt let me take a picture of cmd?)
Now you should see the code you just made... press enter
Your minecraft client should open after about 5 seconds and your done!