iMac won't read files on external hard drive

I got an external hard drive (320GB iomega) to transfer my PC files over to my new iMac. I formatted it properly for both computers beforehand, and had it working on both computers b/f uploading my PC files. All my files , including documents, itunes, photos, as well as converted Outlook contacts, calendar and emails (via O2M app) were saved onto my ext hd before i ejected it from my PC.

When I got it hooked up to the Mac, it would only show my root folders, and the only folder with any files in it was itunes. All other folders (My Docs, My Photos, Calendar, Mailbox, Contacts...etc) are EMPTY. I went to "Get Info" and it shows 40GB used, so the files are on there, but the Mac is not reading them.

What am I missing here?

Thanks,
Mary