How do I open the case?

I have an old Dell Latitude C400 that has some internal problems, either no fan or one that doesn't work, no USB port and the card slot needs to be replaced. I've been told that there are some kind of latches under two of the number keys (At this moment I don't exactly remember which ones) and I have to release those to open the case. Well, I think I found the spots, but pressing those spots doesn't open the case. What am I doing wrong and how do I remedy the situation and finally get the case open so I can see if I can fix the internal problems?