Most notebooks that claim to have one memory expansion slot actually have two, though the second one may be inaccessible under normal circumstances. But if you're happy disassembling the notebook, the second slot will be the same electrical distance, and roughly the same physical distance, from the memory controller as the visible expansion slot. In practical terms, this means if the visible slot is accessed by a cover underneath the computer, the hidden slot may be on the other side of the motherboard, i.e. under the keyboard. It's always worth poking around. After backing up, of course.
