1 (re: Crooked Account Books) - if the government knows you have accounting books, they can force you to turn them over. You must provide them with physical access to the books. In your example, you could take the hard drive out of your laptop and hand it to them. However, if your hard drive was encrypted, and you had the encryption key memorized, you would not have to tell them. If the judge hearing your case did not understand the intricacies of Fifth Amendment doctrine, like the judge in this case, he might order you to decrypt the hard drive. In this case, your lawyer would ask the judge to stay (i.e., delay) his order to give you a chance for interlocutory appeal.

If the judge did not grant the stay, you could turn over the key but explain that you were not waiving your Fifth Amendment rights. Then when you were found guilty, you could appeal, argue that your Fifth Amendment rights were violated, and get your conviction overturned. Alternatively, you could not turn over the key, go to jail for contempt, and wait for your lawyer to appeal the contempt finding and get you out of jail.

2 (re: password vs. physical key in secret place) - in some cases, the act of producing a physical key may actually be protected under the Fifth Amendment. If the police can show that you know the key's location, then by forcing you to produce the key they are not forcing you to give any testimony, and you have no Fifth Amendment protection. However, if they ask you for a key but can't prove that you have it, they are asking you to create implicit testimony. The implicit testimony is "I know where the key is." If this testimony would end up incriminating you, the it is protected by the Fifth Amendment and you don't have to produce the key.

isnt the simple point of the 5th supposed to be more or,ess "you do cannot be compelled bylaw to help convict yourself)... ay law to the contrary would be unconstitutional.

No, the point of the 5th is that you cannot be compelled to give testimony against yourself (which is under oath and for which you will go to jail if you perjure yourself.) You are not protected from helping to convict yourself if you leave the evidence of your crimes available to the court. An encrypted drive is being considered as something like an un-crackable safe for which you have the combination; providing the password is not testifying, it is providing the court access to evidence that you would otherwise be concealing from a valid warrant.

Providing the password to a safe that contains incriminating documents actually is testimonial in nature because it requires you to disclose information you have in your mind (see above). As such, any information that the government obtains by compelling you to give them the password cannot be used against you in a criminal trial. The judge in the case being discussed here got it wrong, and his decision will be overturned on appeal if it goes up to the Supreme Court.

But as the article mentioned:

"Prosecutors in this case have stressed that they don't actually require the passphrase itself, and today's order appears to permit Fricosu to type it in and unlock the files without anyone looking over her shoulder."

So the state is arguing that they're not demanding the password, only the plaintext.

Still seems fishy, but it's not clear that it's testimonial.

I suppose one could argue that it's more akin to a judge demanding that you produce the corpse the police have so far been unable to locate.

Better still, as someone else said, it's like the police demanding that you translate notes you wrote down in your own made-up-and-known-only-to-you language.

The production of decrypted plaintext by means of an encryption key stored in your mind falls squarely within the rule on production of documents from U.S. v. Hubbell, discussed in jpol's comment above. It therefore seems quite likely the state will lose on appeal.