Help required - moving drupal site off server to localhost on Linux laptop

Hi all, I'm a drupal newbie and not super technical. Working as a part-time web assistant in Manchester and the role is requiring more technical knowledge than I have so would really appreciate some help! Basically the organisations current site has been recently migrated to Drupal and is installed on an old server which is unable to cope with the current basic and user-unfriendly site we have, not to mention the additional functionality I want to install with new modules and themes (lots of other stuff living on the server aswell). Due to the vagaries of internal politics I don't have direct access to this server, just FTP. I want to migrate the existing site to localhost on my Linux (Ubuntu 10.4) laptop before making upgrades and changes and then transferring to a 3rd party hosting provider once done.

I have installed LAMP via command line as recommended by online tutorials and a fresh drupal install worked for me. However when I try to migrate over the existing site it isn't working. http://127.0.0.1/drupal throws up the following Server Error 500:

"The website encountered an error while retrieving http://127.0.0.1/drupal/. It may be down for maintenance or configured incorrectly.
Here are some suggestions:
Reload this webpage later.
HTTP Error 500 (Internal Server Error): An unexpected condition was encountered while the server was attempting to fulfill the request."

There is probably a simple solution to this but as a newbie I'm not sure what's going wrong. Would really appreciate some help here, via IM or in-person (amazing!).

Thanks in advance!
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