Hi All, first of all, thanks for the help.

> If you just want to switch a running system, I *think* this would be all 
> you need to do.
> 
> 1 - Point Yum to look at SL yum repositories
> 1a - rm -f /etc/yum.repos.d/*repo
> (a bit drastic, but if you want to go slow, just move everything)
> 1b (SL4) - rpm -Uvh 
> http://ftp.scientificlinux.org/linux/scientific/4x/i386/misc/RPMS/yum-conf-latest.SL.noarch.rpm 

Done.

> 2 - Replace the following packages:
> yum (from centos) -> yum (from SL)
> centos-release -> sl-release
> centos-release-notes -> sl-release-notes (SL5 Only)

I cannot seem to install yum: I get dependency errors:
================
# rpm -i yum-2.4.3-10.SL.noarch.rpm
warning: yum-2.4.3-10.SL.noarch.rpm: V3 DSA signature: NOKEY, key ID 
82fd17b2
error: Failed dependencies:
	python-elementtree is needed by yum-2.4.3-10.SL
	urlgrabber is needed by yum-2.4.3-10.SL
================
So I attempt to follow the dependency trail, and end up stalled at:
================
# rpm -i yum-2.4.3-10.SL.noarch.rpm python-2.3.4-14.7.el4.i386.rpm 
python-elementtree-1.2.6-4.i386.rpm urlgrabber-2.9.6-1.noarch.rpm
warning: yum-2.4.3-10.SL.noarch.rpm: V3 DSA signature: NOKEY, key ID 
82fd17b2
warning: python-elementtree-1.2.6-4.i386.rpm: V3 DSA signature: NOKEY, 
key ID a7048f8d
error: Failed dependencies:
	libdb-4.2.so is needed by python-2.3.4-14.7.el4
================
As far as I can tell, libdb-4.2 is provided by the package compat-db in 
SL5, however, the latest version in SL4 is < 4.2... (I am attempting to 
convert to SL4) Am I missing something here?

Previously I had converted this system from EL4 to Centos4 - might this 
have something to do with it?

Thanks again!
-Chris