Reverse engineer an encryption algorithm

I have a program that encrypts files... I need to know the encryption algorithm and key used in the encryption process. I have a feeling it's using a Blowfish encryption, not a custom algorithm that actually needs rewritten. Furthermore, I've been able to locate a call to an Encrypt function in OllyDBG but can't figure out how to break on it.

I don't expect it to take more than an hour for someone who knows what they're doing.