> The first batch of the minis have smaller heatsink thean the last versions.
> AFAIK 1.25GHz and most of the 1.33GHz version has a smaller heatsink,
> while the rest have bigger.

1.25 and 1.42 GHz models are the older ones. They were later silently replaced by the 1.33 and 1.5 GHz models.

http://en.wikipedia.org/wiki/Mac_Mini#Specifications