There are two types: wedge and desktop types:
Wedges are usually the A500, A500+, A600 or A1200.
The A600 is distinctive as it has no numeric keypad.
A500, A500+ is the largest and the oldest shapes.
The A1200 is newer and is much narrower than the A500.
It may tell you what model it is due to legend on the top right near the floppy drive.
When you boot up, it will ask for a Workbench disk and possibly the Workbench version required e.g. 1.3, 2.0 or 3.0 or 3.1.
The A600 and A1200 have a small IDE port inside, so you can easily add a 2.5" or a 3.5" (with some modification) drive.
I stuck with 2.5" as they fit nice and smuggly and don`t require extra power. They also have PCMCIA Card slots on the left hand side.
An A500 has no hard drive controller, so they usually are added via an extra box on left hand side via expansion port.
They are difficult to get hold of now.
Let us know which model you have so we can advise further.
