First, on the computer from which you want to share the file, open the HomeGroup control panel.
If a homegroup does not already exist (Windows may have created one automatically when you first set up Wi-Fi), click Create a HomeGroup.
Choose the file types you’d like to share (‘Documents’ is not selected by default), and click Next.
You’ll receive a password for the homegroup. Write it down.
Wait a few minutes for Windows to update everything. Then, on the other computer, open the HomeGroup control panel, and you should see the homegroup you just created.
Click Join now and follow the rest of the steps in the wizard. The computers will share files with each other from now on.
To find the shared files, in Windows Explorer look for your homegroup in the left pane. The other computers that you have added to the network will be listed there, and the shared files will appear in the right pane.
If you ever wish to change your homegroup password, open the HomeGroup control panel on a machine that is already in the group, and click Change the password.
Accessing files on a Mac from a Windows 7 PC
On the Mac, visit System Preferences and open the Network application.
Click the WINS tab.
Change the ‘Workgroup’ setting to the same Workgroup your PCs use. (If you’re not sure of the name, you can find this setting listed in your PC’s System control panel.) Click OK.
Still in System Preferences, open the Mac’s Sharing application. Place a checkmark next to File Sharing.
Over in the Shared Folders pane, select the folders you wish to share.
In the Users pane, give rights to each folder as appropriate, assigning either Read Only or Read & Write to the ‘Everyone’ group.
Next, click Options and then put a check in the box for Share files and folders using SMB. Click Done.
Lastly, open the Accounts application, unlock your system, and click Guest Account in the left pane. Check the box next to Allow guests to connect to shared folders.