crash

Wanted to play to see if we (husband and I) wanted to buy the game but I restarted my comp because game had lag and now it gives me this message:

Minecraft has crashed!      
      ----------------------      

Minecraft has stopped running because it encountered a problem; Failed to start game

A full error report has been saved to C:\Users\Student\AppData\Roaming\.minecraft\crash-reports\crash-2013-04-13_23.04.09-client.txt - Please include a copy of that file (Not this screen!) if you report this crash to anyone; without it, they will not be able to help fix the crash :(



--- BEGIN ERROR REPORT 397a26f --------
Full report at:
C:\Users\Student\AppData\Roaming\.minecraft\crash-reports\crash-2013-04-13_23.04.09-client.txt
Please show that file to Mojang, NOT just this screen!

Generated 4/13/13 11:04 PM

-- System Details --
Details:
	Minecraft Version: 1.5.1
	Operating System: Windows Vista (x86) version 6.0
	Java Version: 1.7.0_17, Oracle Corporation
	Java VM Version: Java HotSpot(TM) Client VM (mixed mode, sharing), Oracle Corporation
	Memory: 6665272 bytes (6 MB) / 48967680 bytes (46 MB) up to 259522560 bytes (247 MB)
	JVM Flags: 1 total; -Xbootclasspath/a:C:\\PROGRA~1\\Java\\jre7\\lib\\deploy.jar;C:\\PROGRA~1\\Java\\jre7\\lib\\javaws.jar;C:\\PROGRA~1\\Java\\jre7\\lib\\plugin.jar
	AABB Pool Size: 0 (0 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
	Suspicious classes: No suspicious classes found.
	IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
	LWJGL: 2.4.2
	OpenGL: ATI Mobility Radeon HD 3450 GL version 2.1.7417 Release, ATI Technologies Inc.
	Is Modded: Probably not. Jar signature remains and client brand is untouched.
	Type: Client (map_client.txt)
	Texture Pack: Default
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: ~~ERROR~~ NullPointerException: null

java.lang.NullPointerException
	at javax.imageio.ImageIO.write(Unknown Source)
	at bip.b(SourceFile:278)
	at bis.b(SourceFile:154)
	at bgf.d(SourceFile:350)
	at net.minecraft.client.Minecraft.a(SourceFile:298)
	at avv.a(SourceFile:56)
	at net.minecraft.client.Minecraft.run(SourceFile:507)
	at java.lang.Thread.run(Unknown Source)
--- END ERROR REPORT 68386baa ----------

with this to go to
C:\Users\Student\AppData\Roaming\.minecraft\crash-reports\crash-2013-04-13_23.04.09-client.txt