WordPress MU

Hello.

I need upgrade one installation of WPMU from release 1.2.4 to 2.6.2

with the direct upgrade the blog doesn't work , so I'm looking for the old version, (like 1.3 and 1.5 ), for to try to arrive at the last version .
Someone can help me where I can find the old version ?
Thanks .

Marco

http://trac.mu.wordpress.org/browser/tags

There's a zip at the bottom of each folder.