[CentOS] Enabling MD5 (longer passwords) after installation?

I have noticed on a Centos 4.3 server where I had set some >8
characters passwords for some accounts, that only the first 8
characters are needed (if I forget or mistype the others I login
all the same). 

Can I "move" the live, running system to longer passwords, and how?
or is a reinstall necessary?

TIA,
	Marco


-- 
Marco Fioretti                    mfioretti, at the server mclink.it
Fedora Core 3 for low memory      http://www.rule-project.org/

Man becomes truly man only by passing beyond himself.
				   Paul VI,    POPULORUM PROGRESSIO