Windows 7: Access Denied opening file in shared folder, lock on the icon

Files on the host machine have a lock on them, but not all of them. Network users get an Access Denied trying to open those files, when they could open them a few days ago. I get Access Denied trying to view or edit permissions on some of those files with the lock, but not all of them. It's just on one USB hard drive.

I have a hard drive shared on the network so everyone can watch the video files on it. A bunch of my files got the lock on them 2 days ago, and changing the permissions isn't removing it. The parent folder is shared and every user on the network has access, but the files aren't openable over the network, only on the hosting machine itself, and my user account on the computer attached to the TV.

I detached the hard drive and took it to a friend's house to give him some video files. He couldn't open the folder on his Windows 7 machine, while other friends of mine have had no trouble in the same situation. He took ownership of the folder on his machine and I had to take it back when I got the drive home, and some folders are giving me an access denied error even opening them on the Administrator account on my own machine, and trying to change permissions says access denied.

I can fix the permissions by running the drive through Ubuntu and copying the files to another drive from inside Linux to strip the permissions off, but it's a nearly full 2 TB USB drive and it says it will take about 30 hours to copy the files back and forth to strip those permissions, which means my machine can't be booted to Windows and running as the file server during that time.

I need an in-Windows solution to cure this permissions problem. I never had this trouble with XP, and I know how to work users and groups with NTFS permissions from my MCP training. Something changed in 7 and my Windows 7 Pocket Administrator's Consultant is no help.