Upgrading Drupal

Hi, I must to upgrade Drupal from a semi abandoned site, so it must be very out of date. I wanted to search information about how to upgrade but ups! I didn't remember the Drupal version I have installed in this site.
Can I know it?
By the way, what should be the steps to upgrade? I think is a 4.7.X version,

Thanks!

After upgrdeing from 4.6 to 5.0 I get this error message when trying to access administer pages.

Fatal error: Call to undefined function: _taxonomy_depth() in /export/vol1/unix/p/perra/public_html/arlov/includes/common.inc(1339) : eval()’d code on line 8

I changed the theme for admin and after thats i can't access the administer pages any more. How do i fix this?

Some wierd stuff is happening.
I upgraded to 4.6.10 and now the PHP code in one of my pages that accesses CGI parameters is not working; actually it still works for anonymous users, but it fails for users that are logged in.

The code is not throwing an error, it is just leaving my variables empty.

Here is my code snippet:

I have been used in 4.7 to using <!--break--> in posts to control the teaser. This does not work on my 5.0rc1 installation. What am I missing?

Thanks

I update from 4.7 to 5 but i did not saw modules where still not ready it giveme some trubles. I extract some modules to avoid the problem , but now the web puts this error message::

I recently upgraded my server to php 5.2 which I understand isn't supported right now, however, the errors I am getting do not appear to be related to the session problem.

I have attempted to upgrade my drupal version to 4.7 and 5.0-rc1 however, I am getting a huge number of errors on the site. The biggest problem is that the site appears to be displaying a bunch of binary (the best way I can describe it). I have left it in its current state if anyone can take a look for me: http://www.geeksv.com/

The current version I have tried is 4.7-dev but this problem is happening with every version, I am fairly certain it isn't a database corruption, I have done some checks.

If you don't wish to take a look there here is what I am getting on the front page:

Warning: ini_set() [function.ini-set]: A session is active. You cannot change the session module's ini settings at this time. in /usr/home/geeksv.com/public_html/sites/default/settings.php on line 109

Warning: ini_set() [function.ini-set]: A session is active. You cannot change the session module's ini settings at this time. in /usr/home/geeksv.com/public_html/sites/default/settings.php on line 111

Warning: Cannot modify header information - headers already sent by (output started at /usr/home/geeksv.com/public_html/sites/default/settings.php:109) in /usr/home/geeksv.com/public_html/includes/bootstrap.inc on line 534