The hard disc lives in here. It had about a 200MB disc when I bought it, but this died a death in February 1999 just as I was completing my undergraduate dissertation. I can't remember how much the replacement cost - in those days you did still replace inside parts of things, instead of consigning the whole lot to landfill and buying new - but its capacity was, and still is, 3.2GB.
In its latter years as the main BeebMaster PC, say between 2001 and 2003, the hard disc worked loose if I moved the machine about anywhere, so I had to take off the panel regularly to re-seat the drive. Eventually the head on the screw wore away and the hole in the panel cracked, so it was no longer possible to fit the panel to conceal the hard drive.
The drive now has a sheet of paper underneath it for insulation, because the small board which you can see in the picture, which plugs into the disc with one set of connectors, and then plugs into the laptop's main board with another connector, had become so loose that it no longer kept the drive raised off the board, and without the insulation it was causing electrical problems.