Can access network-shared HDD on a Windows PC, but no content in folders

Hi, so my brother and I share a lot of external HDDs, all of which are connected to his Windows XP PC. A few days ago, he bought a new one, and I can access it perfectly from Finder, I see all the folders, but when I click on a folder, none of them seem to have any content (it says "0 items", I even waited once for 15 minutes to check if maybe it was a load issue, but it isn't).

We subsequently tried to reshare 10 times or so, we even changed the drive letter, we restarted both computers, ... nothing. All of the other drives work fine.

Any ideas? It's really quite annoying, because our music is on it.

Thanks in advance.