Windows 7: can't open documents of a PC in a LAN

Hey guys I have a problem, I have 3 computers connected to a LAN, two laptops via wireless, and a PC (Gateway). But I have a problem. I want to able to see one disk where is important information in the PC from the laptops But I can't, evertime I try to open it it get me this :

Windows cannot access\\Gateway-pc\j
you do not have permissions to access\\Gateway-pc\j , contact your network administration to request access.

I'm able to see information of my laptops from the PC (Gateway) but backwards I can't. I've granted permission for the two laptops from my PC, I've tried this way also \\Gateway-pc\j$ and it asked me for a password I found the password in my PC (Gateway) and I type it in the laptop but still it tells me that I don't have permission to access into the disk.

I need help.

thank you