-- System Details --
Details:
    Minecraft Version: 1.8.1
    Operating System: Windows 7 (amd64) version 6.1
    Java Version: 1.8.0_60, Oracle Corporation
    Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
    Memory: 128814688 bytes (122 MB) / 213909504 bytes (204 MB) up to 947388416 bytes (903 MB)
    JVM Flags: 0 total;
    IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
    Launched Version: 1.8.1
    LWJGL: 2.9.1
    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)
(21:02:13) Game >> #@!@# Game crashed! Crash report saved to: #@!@# C:\Users\fiona\AppData\Local\ttyh_minecraft\client_default\prefixes\1.8.1\crash-reports\crash-2015-10-09_21.02.13-client.txt
(21:02:13) Game >> [21:02:13] [Client Shutdown Thread/INFO]: Stopping server
(21:02:13) LauncherWindow >> Game process finished!
(21:02:53) LauncherWindow >> Error: not null game exit code: -1
(21:02:53) LauncherWindow >> Main window showed

Сrash Report
---- Minecraft Crash Report ----
// Don't do that.

Time: 06.10.15 20:08
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:252)
    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 bss.an(SourceFile:526)
    at bss.ak(SourceFile:355)
    at bss.a(SourceFile:302)
    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:252)
    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 bss.an(SourceFile:526)
    at bss.ak(SourceFile:355)

-- Initialization --
Details:
Stacktrace:
    at bss.a(SourceFile:302)
    at net.minecraft.client.main.Main.main(SourceFile:124)

-- System Details --
Details:
    Minecraft Version: 1.8.1
    Operating System: Windows 7 (x86) version 6.1
    Java Version: 1.8.0_60, Oracle Corporation
    Java VM Version: Java HotSpot(TM) Client VM (mixed mode), Oracle Corporation
    Memory: 60670104 bytes (57 MB) / 105443328 bytes (100 MB) up to 259522560 bytes (247 MB)
    JVM Flags: 0 total;
    IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
    Launched Version: 1.8.1
    LWJGL: 2.9.1
    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)