Strange... folders are there but I can't see them.?

I use an external 1TB HDD Seagate. I have around a 100 GB of Data in folders, that I can not see at all! They are NOT hidden. I can easily see them through WinRAR. I've run all virus scans, no virus at all. Funny thing is, when I copy the folder and paste it in some drive through WinRAR, it copies, BUT IS STILL INVISIBLE! I search for the files and I get it, but why can't I see the folders? I umed that the folders were made invisible, but it's not even that. So what's the problem exactly? It's like Harry Potter wearing an invisibility cloak, and also something with which you can't even feel him... so he's very much there, but you can't touch/see him. WHAT DO I DO?