How can I look in a sharing folder of another computer?

I have a home network of 4 computers - 2 WinXP, Vista, Win7. The network
works normally. I can easily look in a sharing folder of another computer by
my Total Commander. But I made a bootable BartPE CD. After booting from the
CD I can get online and browse any sites around the world, but I cannot look
in a nearby computer folder! Every time I get the following message.

"Workgroup is not accessible. You might not have permission to use... "

How do I fix this problem?

Thank you

Lev