network sharing problem

im connected to a domain, and i have problem with file sharing.

i already checked the domain name or the workgroup they belong, but when i try to access the shared folder from user1, its asking for a password and that would be the administrator username and password and vice versa.

is that with the ip configuration that i put in every pc? or do i have to enable the DHCP and put the DNS?

after that i can acces the shared folder but in the morning the same problem appeared again.

any help would be appreaciated.