Can't access other computers on intranet with windows XP Professional

I have a linksys intranet system, and am using four
comptuers in a home office. My two computers (XP home
and Windows 98) communicate. However, the XP
Professional does not permit the others to share files.
I get this message from my work group folder when trying
to access the XP Professional from other computers:

"Laptop is not accessible. You might not have permission
to use this network resource. Contact the administrator
to find out if you have access permission."

When I try to communicate with the other two computers
from my laptop (XP Professional) I get the following
message:

"MSOFFICE is not accessible. You might not have
permission to use this network resource. Contact the
administrator to find out if you have access permission."

I have spent days trying to figure this out. Any ideas
how I, the administrator of all these computers can
give "permission" to the others to share files?

Thank you

Ron