Required signup?
 

I will be offering free web hosting soon except I would like the accounts to signup at my forum first before being able to signup.

http://www.hostfreeweb.com does this, I'm not sure what they use, knowing they are using IPB, anybody know of a way this could be done or is there a modification somewhere?

One way would be to make the sign up page use vB, like in
https://vborg.vbsupport.ru/showthread.php?t=98009
Then, you could make the sign up page show an error message (using template conditionals) if they aren't logged in, and you can also put their forum username or userid into whatever signup form you use so you can associate the two.