Industrial-strength deterence in the form of an IBM Aptiva

I am frustrated. I have an old IBM Aptiva which houses an ancient Pentium 200. The old Aptiva is housed in an industrial-strength chassis. Heavy, impenetratable, and likely to withstand hits from RPGs. Try as I may, I just cannot not prise the solid metal covers from the casing. I need the information in the hard disk inside the casing.