2 different registration forms

You have two options here.

1. If Job Seekers and Companies are stored in the same database table you can add a simple Lookup field with two values (JobSeeker/Company) and us the same registration form for both types of users.
   
2. If Job Seekers and Companies are two different tables you can have a switch somewhere on your main page like:
   
   Register as a company
   
   Register as a job seeker
   First link should point to companies_add.php, while second should point to jobseekers_add.php. This is it.

1. If Job Seekers and Companies are stored in the same database table you can add a simple Lookup field with two values (JobSeeker/Company) and us the same registration form for both types of users.
   
2. If Job Seekers and Companies are two different tables you can have a switch somewhere on your main page like:
   
   Register as a company
   
   Register as a job seeker
   First link should point to companies_add.php, while second should point to jobseekers_add.php. This is it.
   

Thank you for your reply!
Option one is the one I'm trying to work on, but the thing is some fields should not appear on JobSeeker form and others should not appear on Company form...
However, option 2 would be ideal! the only problem is with the Security settings of the application, there I'll have to specify one table for username and password, I know I can have a user_id field in Companies and Jobseekers tables, and keep the users table light with username and password and email, but in this case, I'll face another problem in the registration page, registration will have to be done in 2 steps...

1. If Job Seekers and Companies are stored in the same database table you can add a simple Lookup field with two values (JobSeeker/Company) and us the same registration form for both types of users.
   
2. If Job Seekers and Companies are two different tables you can have a switch somewhere on your main page like:
   
   Register as a company
   
   Register as a job seeker
   First link should point to companies_add.php, while second should point to jobseekers_add.php. This is it.
   

Will I face any problem if I simply duplicate the registration files and customized each one?

I think this can be a candidate for a new feature in the next release! allowing users to have multiple registration forms...

This question doesn't make any sense.
If you store all registration data in one database table - you can use a single registration form with simple JobSeeker/Company switch.
If you want to store data in two diffeent tables meaning Company and JobSeeker need to fill different set of fields - there is nothing to duplicate as form are supposed to be different.

I'm trying to use the "Registration" pages created by PHPRunner, to benefit from the double opt in and the password reminder etc...

That's the registration page I want to duplicate since I can't use one registration page with a simple switch between Companies and Job Seekers, each of these need different fields for registration.

If these two forms have different set of fields - what exactly you want to duplicate?

Well 70% of the fields are in common, so in the table, I have all the fields for both Companies and Job Seekers, and in the pages I use the ones I want for each registrant...that's why I want to duplicate it...