Accessing PC Harddrives From iMac

Hi all, not sure if this is right discussion areas, but hoping someone is able to assist me.

I have a iMac (Mountain Lion) and a PC (Windows 7 Ultimate) on the saame wireless home network, bith connected under the same workgroup. I've managed to get access to some of the folders on the PC from the iMac, but am stuck at accessing other harddrives on the PC.

My Windows 7 PC is setup as:

1. C:/Drive - operating system and core programs with a computer name of OFFICE-PC
2. DATA Drive - documents and working files
3. MUSIC Drive - music collection
4. PHOTOS Drive - photo collection

The network pathnames of 2-4 are \\OFFICE-PC\Data or \\OFFICE-PC\Music or \\OFFICE-PC\Photos

I'm trying to connect via iMAC CMD+K - Connect to Server and m typing the server name as: smb://OFFICE-PC/Data

All I'm getting is a message from iMac saying "There was a problem connecting to the server "office-pc". You do not have permission to access this server"

I'm at a loss and appreciate any help / guidance someone could give me.

Thanks

Darrran