You need to put your Mac in the same workgroup as your Windows PC. To do this open “Directory Access” (Applications > Utilities > Directory Access). Click on the padlock in the bottom left corner to make changes; you will be prompted for your password. If “SMB” is not ticked off, then tick it off. Select “SMB” and hit the “Configure…” button. Now enter the name of your Windows workgroup.
Source: MacRumours