Solved Windows 95 / 98 Goes To DOS Command Prompt On Startup

We had an old working Quantex computer that ran windows 95 (possibly windows 3.3). A few years ago, the motherboard stopped functioning properly and we could not start up the computer. Recently, I took the hard disk out of the old computer and put it in a Dell computer that runs Windows XP. When I pressed the power button, the screen that displays the computer’s information came on, but immediately switched to a black screen that said “Starting MS-DOS…” It then prompted me to input a command (C:\…). What do I do to make it run the windows 95 operating System?
(I’m not that fimiliar with older computers and MS-DOS)