How to get Minecraft Forge working For Minecraft 1.4.2
1.I recommend a program called mod-tools:Skydaz.com
Un-Zip it and run the .EXE
2.get Minecraft Forge Universal and Forge Modloader [acts like modloader]
3.Run Mod Tools.EXE, while its loading, rename the zip file you downloaded [Forge] to jar.
4.Select Install mod and select the zip file that you just renamed [Forge] and let it install.
5.Run Minecraft to generate the files you need.
6.Now it depends, Some mods go in the Mods Folder, and some go in the Jar.
Follow the instructions that the developer of the mod says to do, if that does not work,
post in the comments your problem, and your crash report.