Module development and code questions

I'm wondering if theres a way to hook into the Drupal user registration process in such a way I can affect the process itself. Here's basically what I'm trying to do:

I'm building a World of Warcraft guild website, and I've decided to take my time and create some custom modules that interact with the games resources. I'm attempting to make them generic and configurable enough that I can post them here as modules available for the public. The module I'm working on now I want to hook into the user registration process so when a user signs up, it connects to a service called the World of Warcraft Armory to verify the username they are signing up with actually belongs to the Guild the website is for.

In my example, say my character's name is "Toblerone" and I'm in the guild "Mechanical Squirrels" on the server "Skywall." The World of Warcraft Armory allows me to type in that character name Toblerone, select the server Skywall, and it will tell me the guild he belongs to, in this case Mechanical Squirrels. I want my module to connect via cURL, or just plain old sockets to the Armory site, grab that XML data, verify that when Toblerone signs up for the Mechanical Squirrels website, he's in the guild Mechanical Squirrels.

We are using the refine_by_taxo module on our site.

It works great, except that on some pages it only shows the first 3 taxonomy terms for the listed content and it seems to ignore the rest.

I have tried changing the settings for the block but nothing seems to work.

Any ideas?

Thanks

I would like to change where the text says ""Attachment" to "View Image" when you go and view a single classified ad. I have been looking but I think it might be in the durpal core?
Thank you for any help.

I'm using Acidfree Albums, and I want an ajax image pager, what shows thumbnails on place of numbers (a horizontally scrollable div). Is there any existing pager or something like this?

Is there any way to replace username (login name) with email?
E-mail is unique too, this is the reason why I don't need the username...
I want only a profile field (full name), which is required and themed in as username.

Hi All I need help regarding Video Streaming. I am using drupal 5. I am trying to create Thumbnails of a video .I have already Installed FFmpag but somewhere i am wrong so please tell me the right way to create thumbnail of a video .and what should be proper setting in video module ....

Thanx
Gaurav