Accounting software

Hello All, I have a friend who has been stuck on Windows because of being tied to being able to hand his accounting data to the accountant in a Tax Office approved format, which has meant Quicken/QuickBooks or MYOB. I am not so certain of legal requirements, but what double entry accounting packages are there, and are any approved? I do know of GNUCash, but not the current status, and is it available for him to play with first on Windows. I an constantly annoyed by the insistence that only commercial packages are valid, when the quality of the coding is demonstrably dubious, let alone whether there are any "back doors". Regards, Mark Trickett