SD Card won't work/plug in nothing happens.

Hello,

I plug in my sand disk 4GB into the proper slot and it does nothing in my dell. I plugged it into my HP and it works but the HP has an ethernet problem so it won't do internet and I need to send pictures. I assume i have a card reader but have no idea how to see. We have kodak easy share on the dell. We have HP Photo Smart on the HP. Is that the problem. Help.