Installed ubuntu on a portable hard drive, can you help me solve problems with hardware?

I have Dell Studio 1535. 3gb ram, Core 2 Duo 2Ghz, 250gb HDD, ATI 256mb graphics card etc.

I have a small portable hard drive, 30gb. I managed to install ubuntu on in along with grub so that it wouldn’t interfere with my system when its not plugged in.

That worked fine apart from the fact that it says “No boot sector found on usb device” or something along those lines. But I can boot it when I choose one time boot and select it.

So I could probably live with that, except it will not let me use the wireless. Currently plugged in with the ethernet cable. I can’t download things I need using the terminal either while plugged in.

For example “sudo apt-get install vlc” just returns package not found. I don’t know what to do.