I can't access other Computer in LAN with follow message:
\\PC19 is not accessible.You might not have permission...

Find out what the IP address of the machine is and try \\xxx.xxx.xxx.xxx instead of \\PC19

Hi,

I agree with the answers before me, but I want you to try the following steps as well

1. make sure that the drives (c:/ or d:/) are shared for administrative purposes
2. Open your (My Computer) and then click on Tools > Folder options > View> and the last option you will find will be (Use Simple File Sharing) checked, you have to uncheck this option first
3. right click on the drives you are trying to access them from another computer (d:/ etc) and go to Security tab and see if everyone user name is added there or if you have a Security group or username from the domain, that is also fine.
4. If you unchecked the option 2, then you will be able to see the Sharing Tab for the drives, and check if the permission is not restricted or limited through selecting the Sharing Tab where D: drive will be shared as D$.
And the permissions you can see below d$

5. If you can not ping that machine, then means the firewall is on or some other problem.
Make sure that the firewall is off on that computer and then try with the above steps.
Let me know if it didn't work
Ramish