I'd probably count for four, but if it counts as a new installation each time you format, than more than double that. (No more now though, I've got a Mac. 3) I'd assume it's the same for many users here.
I wish I could take credit for this... It showed up in my mailbox about ten years ago.
What Happens When Engineers think too much about Christmas...
The number of computer scientists in a room is inversely proportional to the number of bugs in their code.