NOT ABLE TO ACCESS WINDOWS XP COMPUTERS

[VIKRAM]

I have installed windows XP in all computers in the
network & all were working fine. The resources been able
to share with each others.
All of sudden while accessing one computer on the
network, it was asking for some passowrd to give gain to
access to own resources to other computes, while trying
to access that particular computer from other computers.
Can anybody guide me,

Thanks
Vikram Bhutani.