How to delete 1600 users and 2500 posts? A couple years ago I configured a site with Drupal 6.9, and then I forgot about it. I have 160 pages of users that are all spammers and I need to delete all but 3. Doing this one page at a time is painfully slow due to the MySQL calls (I guess). I also have about 2500 forum posts to delete.  

I'm a little afraid to delete records from the database directly.

I saw a module called "mass delete", but it is for Drupal version 5 and not available for version 6.
You can use Views Bulk Operations, a module that allows to execute bulk operations on nodes, users, comments; it also permits to apply the selected operation to all the nodes, users, or comments using the Batch API. The batch API allows forms processing to be spread out over several page requests, thus ensuring that the processing does not get interrupted because of a PHP timeout, while allowing the user to receive feedback on the progress of the ongoing operations.