Don't have permission on folder

[MoodyM]

My mum recently sold her iMac, and I kept her USB 320GB drive that has her Time Machine backup on it. I can browse the drive in Finder on my MBP, but as soon as I get to her and my dad's user folders (which I want to do to get their photos out for them) I get a red stop sign on the folder and if I try to open them it says I don't have permission.

This also happens if I Cmd + Click Time Machine and choose "Browse Other Disk"

I also tried using cp in Terminal and sudo, but this simply copies the folder WITH the red stop sign.

Any ideas how I can recover my folks' photos and documents?

Thanks