Minecraft has been crashing for me for the past few days, here is the report that the crash window gives me, I hope you are able to work with the information provided.

[20:33:04] [Client thread/INFO]: Setting user: LastofTimeLords
[20:33:04] [Client thread/INFO]: (Session ID is token:c2dd5ddc7b304256a3641d6df2ecc975:0b0f624cd2ed41658d55d480860f5542)
[20:33:08] [Client thread/INFO]: LWJGL Version: 2.9.1
[20:33:08] [Client thread/INFO]: Reloading ResourceManager: Default
[20:33:11] [Sound Library Loader/INFO]: Starting up SoundSystem...
[20:33:11] [Thread-6/INFO]: Initializing LWJGL OpenAL
[20:33:11] [Thread-6/INFO]: (The LWJGL binding of OpenAL. For more information, see http://www.lwjgl.org)
[20:33:14] [Client thread/INFO]: Created: 512x512 textures-atlas
[20:33:16] [Thread-6/INFO]: OpenAL initialized.
[20:33:16] [Sound Library Loader/INFO]: Sound engine started
[20:33:27] [Client thread/ERROR]: Exception reading C:\Documents and Settings\D620\Application Data\.minecraft\saves\Gallifrey 1_8\level.dat
java.util.zip.ZipException: Not in GZIP format
at java.util.zip.GZIPInputStream.readHeader(Unknown Source) ~[?:1.7.0_71]
at java.util.zip.GZIPInputStream.<init>(Unknown Source) ~[?:1.7.0_71]
at java.util.zip.GZIPInputStream.<init>(Unknown Source) ~[?:1.7.0_71]
at fz.a(SourceFile:13) ~[1.8.1.jar:?]
at bql.c(SourceFile:62) [1.8.1.jar:?]
at bqh.b(SourceFile:52) [1.8.1.jar:?]
at bxf.f(SourceFile:87) [1.8.1.jar:?]
at bxf.b(SourceFile:59) [1.8.1.jar:?]
at bxe.a(SourceFile:368) [1.8.1.jar:?]
at bss.a(SourceFile:812) [1.8.1.jar:?]
at bxp.a(SourceFile:216) [1.8.1.jar:?]
at bxe.a(SourceFile:342) [1.8.1.jar:?]
at bxp.a(SourceFile:471) [1.8.1.jar:?]
at bxe.k(SourceFile:405) [1.8.1.jar:?]
at bxe.p(SourceFile:382) [1.8.1.jar:?]
at bss.r(SourceFile:1480) [1.8.1.jar:?]
at bss.at(SourceFile:880) [1.8.1.jar:?]
at bss.a(SourceFile:317) [1.8.1.jar:?]
at net.minecraft.client.main.Main.main(SourceFile:124) [1.8.1.jar:?]
[20:33:27] [Client thread/ERROR]: Exception reading C:\Documents and Settings\D620\Application Data\.minecraft\saves\Gallifrey 1_8\level.dat_old
java.util.zip.ZipException: Not in GZIP format
at java.util.zip.GZIPInputStream.readHeader(Unknown Source) ~[?:1.7.0_71]
at java.util.zip.GZIPInputStream.<init>(Unknown Source) ~[?:1.7.0_71]
at java.util.zip.GZIPInputStream.<init>(Unknown Source) ~[?:1.7.0_71]
at fz.a(SourceFile:13) ~[1.8.1.jar:?]
at bql.c(SourceFile:73) [1.8.1.jar:?]
at bqh.b(SourceFile:52) [1.8.1.jar:?]
at bxf.f(SourceFile:87) [1.8.1.jar:?]
at bxf.b(SourceFile:59) [1.8.1.jar:?]
at bxe.a(SourceFile:368) [1.8.1.jar:?]
at bss.a(SourceFile:812) [1.8.1.jar:?]
at bxp.a(SourceFile:216) [1.8.1.jar:?]
at bxe.a(SourceFile:342) [1.8.1.jar:?]
at bxp.a(SourceFile:471) [1.8.1.jar:?]
at bxe.k(SourceFile:405) [1.8.1.jar:?]
at bxe.p(SourceFile:382) [1.8.1.jar:?]
at bss.r(SourceFile:1480) [1.8.1.jar:?]
at bss.at(SourceFile:880) [1.8.1.jar:?]
at bss.a(SourceFile:317) [1.8.1.jar:?]
at net.minecraft.client.main.Main.main(SourceFile:124) [1.8.1.jar:?]
[20:33:29] [Server thread/INFO]: Starting integrated minecraft server version 1.8.1
[20:33:29] [Server thread/INFO]: Generating keypair
[20:33:30] [Server thread/INFO]: Preparing start region for level 0
[20:33:31] [Server thread/INFO]: Preparing spawn area: 17%
[20:33:32] [Server thread/INFO]: Preparing spawn area: 68%
[20:33:32] [Server thread/INFO]: Changing view distance to 2, from 10
[20:33:33] [Server thread/INFO]: LastofTimeLords[local:E:29045568] logged in with entity id 13 at (-312.48877448998195, 64.0, -181.92489575169898)
[20:33:33] [Server thread/INFO]: LastofTimeLords joined the game
[20:33:38] [Server thread/WARN]: Can't keep up! Did the system time change, or is the server overloaded? Running 4406ms behind, skipping 88 tick(s)
#

1. A fatal error has been detected by the Java Runtime Environment:
   #
2. EXCEPTION_ACCESS_VIOLATION (0xc0000005) at pc=0x30c23060, pid=9112, tid=8676
   #
3. JRE version: Java(TM) SE Runtime Environment (7.0_71-b14) (build 1.7.0_71-b14)
4. Java VM: Java HotSpot(TM) Client VM (24.71-b01 mixed mode windows-x86 )
5. Problematic frame:
6. C [iglicd32.dll+0x43060]
   #
7. Failed to write core dump. Minidumps are not enabled by default on client versions of Windows
   #
8. An error report file with more information is saved as:
9. C:\Documents and Settings\D620\Application Data\.minecraft\hs_err_pid9112.log
   #
10. If you would like to submit a bug report, please visit:
11. http://bugreport.sun.com/bugreport/crash.jsp
12. The crash happened outside the Java Virtual Machine in native code.
13. See problematic frame for where to report the bug.
    #
    AL lib: (EE) alc_cleanup: 1 device not closed