Hey there, fellow Minecrafters!

I have run into a problem whenever trying to play Minecraft on my dad's computer. Both of our computers are pretty much identical, and they both have 2GB of RAM.

My computer is currently "out of commission" so I've been using my dad's, but I just don't understand why I would receive this error...

That's with the World of Minecraft client, but whenever I try from Minecraft.net, it loads everything but then the window turns black and the browser freezes. (I have to end it through the Task Manager.)

HALP Please?