BIG Problem!!!

Please help me!!!

My database on one of my sites has crashed!!! I managed to get my user database back but have lost around 3,000 members.

I want to know how i can import my members that i have left,which is just over 12,000 into my new installation.

My site was running wordpress 2.5 and now i cant import the wp_users database into 2.9.2

plz help!!!