Itunes Store Support

Sorry to hear about the theft, but officially Apple does not allow redownloads of purchased items other than iPhone/iPod touch applications. It's your responsibility to make backup copies (as iTunes itself advises) in case something goes wrong with your system or it gets lost or stolen, as unfortunately it apparently did in your case, and you lose all your content. The official statement of their policy can be found here, among other places. If you don't have a backup of your purchased items, you're probably out of luck and will need to repurchase your content.

If you have your content backed up, post back and someone here can help you get it restored. Otherwise you can try contacting iTunes Store Customer Service (select the "Music Purchases" or "Video Purchases" category, as appropriate, then "Lost or Missing Items". You'll find either an "Express Lane" button - just follow the instructions to get to the contact form - or an "Email Us" button) ") and explaining what happened. Reportedly in some cases Apple has allowed redownloading on a one-time basis. But don't count on it.

As to your last request, there really is no forum where it's safe to post serial numbers, and in general there's no need to do so since everyone here is just a fellow user so we don't need to know your S/Ns.

Regards.

If your tracks and photos are still in MobileMe, you should be able to just connect to your iDisk and copy the items back to your computer. If they're gone from MobileMe, then there's probably no way to recover them, though you can contact MobileMe support and ask if there's anything they can do:

http://www.apple.com/support/mobileme/

Regards.

You can only de-authorize computers to which you have access.

There really is no need to de-authorize.

When you reach 5, then you can deauthorize all and the re-authorize the active computers.

You need to change your passwords.

http://support.apple.com/kb/HT1420

Sorry, but you cannot yourself deauthorize a computer to which you no longer have access. You can try contacting the iTunes Store customer support department through the form at the bottom of their Support page (select the category and subcategory closest to the issue you're reporting) and explaining the problem to them. They might be willing to clear your authorizations for you so you can re-authorize your current system(s).

Regards.