Well, as far as having Mepis and Fedora on separate hard drives, I would just ditch the Fedora. There's nothing you can't do in Mepis that you can in Fedora, it's kinda like having Windows XP and Windows 2k on the same machine... Your network issues. Hmm, first we need some information.
What kind of internet connection do you have? Dial up? Cable? DSL?
Are you connected with a router? Does your router use DHCP to give IP addresses
Is your DHCP server giving your Mepis machine an IP?
You can check this by going to the Mepis OS Center, (K-Button, Mepis OS Center eth0)
Is there a possible IP conflict on your network?
When you boot to Mepis do any error messages pop up?