Saring files and printers

I place a some of new coputers with cleen instal of w2k. At some of workstations I share files and printers and I receive two different results. At some computer I can access that printers trough Explorer or neighbourhood, but at the another computers recive access screen to type UN and PASS. When I instal this printer from C1(share) to C2 I must type UN and PASS trought explorer. When I restart the C2 computer I cant print to this printer, it is not accessible and mus trought explorer conect C1 with UN and PASS. I do not hawe make a extra setings and all computers hawe NTFS. Where is the fake?