Q: How can You authorise your Windows Vista computer??? I do not get this drop down menu nowI cannot get this here, have been trying for hours, why is this so uncooperative? My first impression of I tunes is not so good after that.

Authorize a Mac or PC

Review the following before you authorize a computer:

• You can authorize up to five computers with your Apple ID.
• You must authorize your computer to download past purchases, use Home Sharing, or use the Automatic Downloads setting.
• You can play unprotected music that's in the AAC file format without authorizing your computer. This includes iTunes Plus tracks and content  from sources other than the iTunes Store, like your audio CDs.

To authorize a computer, follow these steps:

1. Open iTunes.
2. Choose Store > Authorize This Computer from the menu bar.
   You may need to show the menu bar to see this option in Windows.     In earlier versions of iTunes, you can access this option from the Advanced menu.
3. Enter your Apple ID and click Authorize.
   If your Apple ID uses an expired MobileMe account, you can still authorize your computer.

In some cases, iTunes may ask you to authorize the computer again. iTunes should use the same authorization as before if the computer is in your  list of authorized computers.

Learn what to do if iTunes repeatedly asks you to authorize when you try to play your content.

http://support.apple.com/kb/ht1420

Note : If you are Unable to see the Store Tab on your iTunes then click anywhere on your iTunes and press

Ctrl + B key on your keyboard once and you should be able to see the Store tab in your iTunes.