Which internet connection is slow? The WiFi should be fine. I don't have experience with nVidia networking cards, so I don't know what to tell you there. Maybe you could try ndiswrapper. EDIT: If the wifi is slow, I recall using that card in the past. I had to use madwifi, otherwise it wouldn't even detect networks. This has been a few years ago though. (I think I was running Mint 7 or
I seem to recall there being an issue with the Radeon 4XXX series and earlier cards on Ubuntu 12.10 and LM14. You will need to downgrade your X-server version, or install LM13. I recommend that latter since Mint 13 is a LTS and will be supported for 5 years. I believe it works fine on the older Radeon cards.
If you want to keep Mint 14, search for tutorials on downgrading your x-server version on Google, or search here for previous posters with the same issue.