[Leaplist] Install Question

[Bruce Metcalf]

Got a question I haven't been able to google an answer to:

When installing Debian 4.2 (among others), I am presented with a screen 
titled "Install the base system". I am then given four choices:

linux-image-2.6.18-5-686
linux-image-2.6.18-5-486
linux-image-2.6-686
linux-image-2.6-486

I have not been able to discover what the difference between these four 
options is, nor how to decide which is most appropriate for any given 
machine.

Any clues on this will be very much appreciated.

Bruce