How do I unlock my iTunes account when my old e-mail is unavailable?
I am afraid you are out of luck and there is no help for this. I tried to help a tech support client with this same problem and there is nothing to be done about it. It is truly too late.
People, if you have ever bought anything from any merchant (not just iTunes) and registered your account with the merchant using an email address from your employer, and that email account is still active, do this:
Get a free email account from Google Gmail, Yahoo, Hotmail, or another free email service.
Log in to each account with a merchant and change your account's email address from your work email address to your new extra email address from Google, Yahoo, etc.
Only ever buy anything on an account that has your free extra email address as the registered email address.
Paul Jackson, I'm sorry you've had to learn a hard and expensive lesson.
Some social engineering solutions :
Your iTunes account was presumably associated with your credit card, yes? You could attempt to prove you identity to Apple via that credit card connection. You could warn them that you plan on contesting credit card charges if they cannot restore the account.
If Apple won't help, then collect your old credit card bills with iTunes charges, and speak with your credit card company about contesting those charges. You're beyond the 60 day period, but maybe not the 1 year "claims and defenses" period. I doubt you'll get your money back, but you have a legitimate dispute with Apple, so stick them the dispute resolution merchant fees, which might cost as much as $30 per song. Do not lie to your credit card company, simply push the dispute process as far as possible, the further it goes the more money they charge Apple.
You could theoretically sue Apple in small claims court. Imho, this sounds like way way too much hassle for a few hundred bucks. But maybe you could get your account back by contacting Apple's legal department in writing.
Two technical solutions :
You say you still have the files themselves, yes? There are a variety of tools for removing iTunes DRM. A priori, I'd imagine most/all require authorization since that's the easiest way, but perhaps some clever one does not. Try any that look promising.
Do you have an iPod? If so, try Graeme Hutchison suggestion. If it only give you encrypted music, then theoretically the iPod knows the authorization keys, meaning you've a slim chance someone discovered a trick for using the iPod's authorization to decrypt your music. Google isn't finding anything for me though.
As an aside, you should never buy DRM protected content in the first palce because : (a) Eventually you'll lose access one way or another, often by the company discontinuing the service. (b) Your supporting the DRM technologies which create these problems. Any books, movies, or music distributed with DRM are also available without DRM if you look.
Try contacting the IT department of that prior employer to see if they will accept and forward a few Apple emails to you for one day.