I remember those computers with the keys for them, If I recall correctly, it was to prevent powering on or off depending on the position. I'd be willing to bet this is using an IDE standard drive based on it's age. eBay would most likely have those. If you have any MS-DOS install disks in your collection, you may be able to format the HDD and get up and running by reinstalling it., unless it's doing the "click of death' or spinning up and then down up then down and so forth.
The turbo button was pretty fun for the time too. IF you were running at 16mhz, you could hit the button and it would boost it to 33mzh or something like that. Sort of for the extra kick you would probably need to compile programs or run a newer game at the time.

