On OS X: Go to Preferences → Sharing and enable file sharing. Go to options and make sure the SMB option is checked and then check your username. Go and share a folder (i.e. right click on a folder and check the “Share” box). Share your home directory if you want it all accessible.
On Vista: Go and type in “regedit.” Make a backup of your registry because messing it up can cause MAJOR problems. This can be done by going to File → Export. Go to HKEY_LOCAL_MACHINE → SYSTEM → CurrentControlSet → Control → LSA → LmCompatibilityLevel and edit this item. The default should be 3 but go ahead and set it to 1. Remember to have some files shared (right click on a folder and check the share box, it might ask you some questions)!
Access Vista from OS X: On your Mac, go to the Finder and hit command + k. Put smb://192.168.0.51 in the server field. Now it might ask you for a username and password and just enter the one that is on your PC for that specific folder.
Access OS X from Vista: Now on your PC, if you type in the explorer window \\IPADDRESS\username it should go to your computer and ask you for a username and password (unless it is the same on your PC). Another way to access it is just to go to the “Start” menu and click on “Network.” Your computer should be listed there.
