MySQL 5.0 install error

[Ts]

Could not install all dependencies

Errors were encountered while processing:
/var/cache/apt.archives/mysql-server-5.0_5.1.30really5.0.83-0ubuntu3_amd64.deb

ProblemType: Package
AptOrdering:
 mysql-server-5.0: Install
 mysql-server-5.0: Configure
Architecture: amd64
Date: Fri Jan 15 18:29:22 2010
DistroRelease: Ubuntu 9.10
ErrorMessage: subprocess new pre-installation script returned error exit status 1
InstallationMedia: Ubuntu 9.10 "Karmic Koala" - Release amd64 (20091027)
NonfreeKernelModules: fglrx
Package: mysql-server-5.0 (not installed)
ProcVersionSignature: Ubuntu 2.6.31-17.54-generic
SourcePackage: mysql-dfsg-5.0
Title: package mysql-server-5.0 (not installed) failed to install/upgrade: subprocess new pre-installation script returned error exit status 1
Uname: Linux 2.6.31-17-generic x86_64

[Jean-Baptiste Lallement (jibel)]

Thanks for your report.

The relevant error is
Unpacking mysql-server-5.0 (from .../mysql-server-5.0_5.1.30really5.0.83-0ubuntu3_amd64.deb) ...

Aborting downgrade from (at least) 5.1 to 5.0.

dpkg: error processing /var/cache/apt/archives/mysql-server-5.0_5.1.30really5.0.83-0ubuntu3_amd64.deb (--unpack):

 subprocess new pre-installation script returned error exit status 1

Downgrading mysql from 5.1 to 5.0 is not a supported operation.
In order to do that you should:
- Backup your data
- Fully uninstall mysql5.1
- Install mysql5.0
- restore your data

I'm closing this report since it is not a bug with mysql.