The same way you share drives in Windows 7 over wire.http://windows.microsoft.com/en-us/windows7/File-sharing-essentialshttp://www.tomshardware.com/forum/32700-42-enabling-file-sharing-windows-windows-vista-machines
Only caveat is, if you want to share between different Windows versions (Windows 7, Vista, XP, etc.), then don't use Homegroups. Homegroups are strictly a Windows 7 feature and only compatible w/ other Windows 7 machines. Use simple file sharing instead.