Q: how do I list authorized computers in iTunes?

There is No List  as such...

If you no longer have, or access to, the computer(s) you want to deauthorise,

Log in to iTunes,  go to "view your account info" on the itunes store,  deauthorise all five, (Please Note: this can only be done Once every 12 months)  and then re-authorize your current Computer(s) one at a time.

Authorise / Deauthorise About

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

Actually once you have signed on to iTunes Account and go to Account Infomation you can see a list under the second section iTune in the Cloud click on the the link called Manage Devices There it lists the devices and alows you to disable each one at a time.

Your answer looks promising for my issue as well.

I couldn't see this when logging into Apple from my Windows workstation through Internet Explorer.

Do I access this information by logging into Apple through iTunes instead?

Just so no one else coming upon this thread gets confused, the answer from Douglas Jones relates to managing what devices can download purchases from iTunes - which you can do per his instructions.

The OP was asking about managing the list of computers that are authorized to play content listed in the iTunes Library. Two very different things.

As AnaMusic stated, you cannot see a list of Authorized Computers, only how many are authorized. I have a Mac, iPhone and Acer laptop that are authorized so my account shows 3 authorized computers/devices. If it said 4, I'd know some unused / work / trashed computer was still authorized and would then choose to "Deauthorize All". Then I would Authorize the appropriate computers. As she stated, you can only Deauthorize All once every 12 months.

That's pretty ridiculous that they won't let you view what's authorised and add and remove them individually.

It's one of the main areas that Apple's software is ridiculously difficult to use. Huge functionality issue.