What I expected to happen was...:
The game to download what it needs when I click play and then lauch the game.

What actually happened was...:
I click play the game downloads stuff for a few minutes.The loading bar is right at the end and then it crashes.
Here is the error report:
---- Minecraft Crash Report ----
// Hey, that tickles! Hehehe!

Time: 20/04/14 16:53
Description: Initializing game

java.lang.NullPointerException: Initializing game
at azd.a(SourceFile:502)
at azd.Z(SourceFile:340)
at azd.e(SourceFile:689)
at net.minecraft.client.main.Main.main(SourceFile:103)

A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------

– Head –
Stacktrace:
at azd.a(SourceFile:502)
at azd.Z(SourceFile:340)

– Initialization –
Details:
Stacktrace:
at azd.e(SourceFile:689)
at net.minecraft.client.main.Main.main(SourceFile:103)

– System Details –
Details:
Minecraft Version: 1.7.2
Operating System: Windows 8 (amd64) version 6.2
Java Version: 1.7.0_17, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 56674328 bytes (54 MB) / 94896128 bytes (90 MB) up to 954466304 bytes (910 MB)
JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx1G
AABB Pool Size: 0 (0 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
Launched Version: 1.7.2
LWJGL: 2.9.0
OpenGL: ~_ERROR~ RuntimeException: No OpenGL context found in the current thread.
Is Modded: Probably not. Jar signature remains and client brand is untouched.
Type: Client (map_client.txt)
Resource Packs: []
Current Language: ~_ERROR~ NullPointerException: null
Profiler Position: N/A (disabled)
Vec3 Pool Size: ~_ERROR~ NullPointerException: null
Anisotropic Filtering: Off (1)