My Minecraft crashed on the startup screen.

Please try deleting the 1.6.4 folder ([minecraft|http://hopper.minecraft.net/help/finding-minecraft-data-folder]/versions/1.6.4) and then redownloading 1.6.4. Does that fix your problem?

Are you sure you can set -Xmx1300M on your computer (32bit OS) ?

Duplicate of MC-22764

Neither of those fixes work and it is not a duplicate of MC-22764.