search for minecraft.jar and delete the file.
login and a new .jar file will download.
You are correct about the mods, but most are done to a high standard but can cause compatability problems. He could delete the mods and try again.
I would suggest using the yogbox mod package.
yogiverse.com/showthread.php?11841-YogBox-A-carefully-chosen-compilation-of-good-mods.
Also from the minecraft forums. support section.
part 3 - Game errors/crashes
Problem: When i launch minecraft i get a black screen!
Solution: If you installed a mod, you probably missed one needed mod (mod loader, audio mod etc..) and now it does not work. To fix this, open the minecraft launcher, press options, and click on force upadte. then start the game, and minecraft will download a fresh copy. next install the mods correctly.
Problem: You installed the mods correctly, but you still get a crash/blackscreen.
Solution: Did you delete the META-INF folder inside minecraft.jar when installing? if not, again, force update, install the mods, and delete META-INF found inside the minecraft.jar file.
Problem: I installed X mods, deleted meta-inf, installed the must have mods, but i still get blackscreens! HELP!
Solution 1: There are mods that must be installed before others, i.e modloader+audio mod+GUI API. you MUST first install mod loader, after that audio mod, and only then GUI API, or else it wont work.
Solution 2: Some mods are not compatible with other mods. this in-compatibility may come from using the same item ID's, modding the same .class file, etc... if the X mods you installed do not work with each other, and you followed the instuctions, they are probably in-compatible. sorry, no solution here. you should point out the mod that does not work with the other one to its creator, so he can try and fix it.