HELP - Internal to external HD - cant access docs/folders

Hi there, Hopefully someone can help me.

My old HD was getting too full and after many years, i got a new 80gb HD to take its place. Nothings wrong with the old one, i just wanted a fresh drive. Windows was installed on it.

New HD bought and installed internally as master drive. Installed windows etc on it....everything is fine and dandy. Old HD is currently an external drive via usb [windows still installed on it. I've basically not touched it].

PROBLEM
I want to take some stuff off my old C drive HD and put it onto my new HD. For example - stuff in My Documents, Stuff from old desktop. But i cant. it says access is denied [from c - docs and settings - user]. And hovering over the User folder it says empty!

Does anyone know how i can access my old drive properly whilst its an external drive? I dont want to switch them as i can't be bothered opening pc - uninstalling and installing etc. [but i guess it could be an absolute last option].

Any suggestions will be welcome:frusty: