Problème de démarrage de Minecraft

Bonjour, jai un soucis avec minecraft... quand je veux le démarrer il me fait un crash report :

des fois il y aussi une fenêtre me disant Lack of updated graphics drivers


---- Minecraft Crash Report ----
// This doesn't make any sense!

Time: 31/05/15 13:00
Description: Initializing game

org.lwjgl.LWJGLException: Pixel format not accelerated
at org.lwjgl.opengl.WindowsPeerInfo.nChoosePixelFormat(Native Method)
at org.lwjgl.opengl.WindowsPeerInfo.choosePixelFormat(WindowsPeerInfo.java:52)
at org.lwjgl.opengl.WindowsDisplay.createWindow(WindowsDisplay.java:247)
at org.lwjgl.opengl.Display.createWindow(Display.java:306)
at org.lwjgl.opengl.Display.create(Display.java:848)
at org.lwjgl.opengl.Display.create(Display.java:757)
at org.lwjgl.opengl.Display.create(Display.java:739)
at ave.ap(SourceFile:534)
at ave.am(SourceFile:363)
at ave.a(SourceFile:310)
at net.minecraft.client.main.Main.main(SourceFile:124)


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

-- Head --
Stacktrace:
at org.lwjgl.opengl.WindowsPeerInfo.nChoosePixelFormat(Native Method)
at org.lwjgl.opengl.WindowsPeerInfo.choosePixelFormat(WindowsPeerInfo.java:52)
at org.lwjgl.opengl.WindowsDisplay.createWindow(WindowsDisplay.java:247)
at org.lwjgl.opengl.Display.createWindow(Display.java:306)
at org.lwjgl.opengl.Display.create(Display.java:848)
at org.lwjgl.opengl.Display.create(Display.java:757)
at org.lwjgl.opengl.Display.create(Display.java:739)
at ave.ap(SourceFile:534)
at ave.am(SourceFile:363)

-- Initialization --
Details:
Stacktrace:
at ave.a(SourceFile:310)
at net.minecraft.client.main.Main.main(SourceFile:124)

-- System Details --
Details:
Minecraft Version: 1.8.6
Operating System: Windows 8.1 (x86) version 6.3
CPU: 2x AMD Athlon(tm) 64 X2 Dual Core Processor 4400+
Java Version: 1.8.0_25, Oracle Corporation
Java VM Version: Java HotSpot(TM) Client VM (mixed mode), Oracle Corporation
Memory: 101762368 bytes (97 MB) / 159789056 bytes (152 MB) up to 523501568 bytes (499 MB)
JVM Flags: 6 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx512M -XX:+UseConcMarkSweepGC -XX:+CMSIncrementalMode -XX:-UseAdaptiveSizePolicy -Xmn128M
IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
Launched Version: 1.8.6
LWJGL: 2.9.4
OpenGL: ~~ERROR~~ RuntimeException: No OpenGL context found in the current thread.
GL Caps:
Using VBOs: No
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)