Access from Windows 7,not from imac

A while back i bought an iMac…cool machine…there is one public folder i can see and use from my windows 7 machine, but from my mac there is a red X…I do not have permission.  There is nothing I can do(it looks like) from the windows machine…the folder is set to public all…

anyone have any ideas?

Hi there, what version of OSX do you have on the iMac? How do you try to access the drive?