Mythic does not want new players for UO, so if you try to use the link that THEY provide on UO.com, you will find that you are prevented from opening a new account at the very last minute by a "this page is unavailable" message.
You have already entered all your personal information, so not only are you unable to open a new UO account, you are left wondering if Mythic (or someone else) has some nefarious purpose for allowing the KR free trial link to remain on UO.com and for collecting your personal information for no obvious reason.
You CAN start a free UO trial, UO Gold, over at Fileplanet, if you can dig up the proper page with the key code. I'm guessing Fileplanet was given UO Gold codes in bulk back when it came out and still have some left over.
I assume they are old leftover bulk codes because I seriously doubt that Fileplanet cares much more than Mythic whether or not UO gets new accounts.