Win7 can't see folders on an external drive

I have a Win7 machine with external drives. I bought a new machine, also with Win7. When I moved the external drives over I can't see the folders. I thought the drive might be damaged so I moved them back to the original machine and I can see the folders.

Why can't I see the folders on the external drive with the new machine?

Do you get any kind of message when you try to browse the external drive, like Access denied?

I just thought of,it, the new machine is 64 bit so not sure what to do now

64 bit does not matter. Please answer my question.