Reinstall Debian when adding drive?

[postid <postid@att.net>]

I have an older machine (Dell Optiplex GS150) that needs more 
hard drive space. I have some nonoperational hand-me-down 
computers from which I can rob a drive. If I keep the original as 
the master and add one of these used drives as a slave, must I 
reinstall Debian Lenny or will Lenny detect the new hardware and 
allow me to mount it, format it, etc.?

postid