Toda vez que tento entrar (depois de tentar colocar mod nele) aparece:

Mods loaded: 1
ModLoader Beta 1.6.6

Bad video card drivers!
-----------------------

Minecraft was unable to start because it failed to find an accelerated OpenGL mode.
This can usually be fixed by updating the video card drivers.



--- BEGIN ERROR REPORT 62fef060 --------
Generated 13/06/11 15:07

Minecraft: Minecraft Beta 1.6.6
OS: Windows XP (x86) version 5.1
Java: 1.6.0_25, Sun Microsystems Inc.
VM: Java HotSpot(TM) Client VM (mixed mode), Sun Microsystems Inc.
LWJGL: 2.4.2
[failed to get system properties (java.lang.NullPointerException)]

org.lwjgl.LWJGLException: Pixel format not accelerated
at org.lwjgl.opengl.WindowsPeerInfo.nChoose… Method)
at org.lwjgl.opengl.WindowsPeerInfo.chooseP…
at org.lwjgl.opengl.WindowsDisplay.createWi…
at org.lwjgl.opengl.Display.createWindow(Di…
at org.lwjgl.opengl.Display.create(Display.…
at org.lwjgl.opengl.Display.create(Display.…
at org.lwjgl.opengl.Display.create(Display.…
at net.minecraft.client.Minecraft.a(SourceF…
at net.minecraft.client.Minecraft.run(Sourc…
at java.lang.Thread.run(Unknown Source)
--- END ERROR REPORT 8a0890a5 ----------

Como posso corrigir esse erro?

tenta desisnstalar e instalar dinovo ou se nao se vc usar windows 7 restaura a pasta do jogo, e tbm pode ser a placa de video atualiza o drive da placa de video conserteza umas dessas alternativas ajudaram