Installing Kubuntu 11.04 after installed Ubuntu 11.04: You already have installed Ubuntu 11.04 but you haven’t liked the Unity. You want to try another window manager like KDE. Check out how to install it.
Installing Kernel 2.6.39 in the Ubuntu 11.04 (Natty Narwhal): Check out here, step by step about how to compile and install Kernel 2.6.39.
How to fix the error “libstdc++.so.6: wrong ELF class: ELFCLASS64″ after installed GCC 4.6: If you compiled and installed GCC 4.6 and during the Android Gingerbread (or another software) compilation you received the following error message: “libstdc++.so.6: wrong ELF class: ELFCLASS64″. Check out here how to solve this issue.