Imported users, deleted when imported more from other site?

[Christian8a]

I imported my users from one of my sites to my main site, then I tried to import another members from other of my sites to my main site and like it replaced the ones recently imported.
After importing the first time i made sure I put the members on the registered users group and deleted the impex usergroups so it should have worked, what am i doing wrong?

[Jerry]

Not removing the import ID's and finalizing the import :

http://www.vbulletin.com/docs/html/impex_multi_import