many blender old versions on the same computer

sorry if my english is very so/so/:spin:I would ask to some of you if I may have on the same computer two or more versions of Blender. I had 2.45 and 2.48,- in an I Mac- but ,after a week,2.45 does not more run it is suddenly close,even with the files that I nade with it last year,and only 2.48 appears as default.someone can explain me why? because I am very interested in older version,but I.m afraid they are going to eat each others. thank you very much.

Download zip files, not installers

I guess one problem will be the .B.blend file.
A few weeks i updated my blender and it crashed on startup, because of the .B.blend.
It was created with 2.47 and now iam using 2.48.

@ColeZero, any links for info?
This .B.blend thing is new to me, I did not realize
this was introduced somewhere at 2.47.
Did anyone try to remove it, or move it to another place
and after running an older 2.45 version - - is it necessary
to put it back … or only a startup-delay when blender creates a
new one?
and last:
Whatabout using different users?
I think this is the only way to avoid the overwriting
of the user-dependant home/.blend directory with the
different scripts (those are sometimes too not compatible
between the different blender-versions).

One bad thing, happened to me, i openend an older blender-file
with a newer version and did save it back without care. That should say
it is not only to make a different setup for the versions, it may
necessary to keep the working blend-files separat too. Then using
different users and saving those things in their own home-directories
would make it easy to keep this things clean.

On windows you can run as many versions of Blender as you like.
As ZanQdo said, just use the zip files, then unzip them into a good location.
You can also use all the versions of python that are needed also.
The best way to do this is to install old versions of python directly into Blender’s main folder.

However, just because you created a file with Blender 2.25,
does not mean that 2.25 will open that file by default.
Generally speaking,
the Blender you installed last or set by yourself or set by your OS as default program to open .blend files,
will be the one that opens the .blend file.
Thus it is best when using multiple versions of Blender,
to Open Blender first, then open the file you need using Blender’s file system. (file/open or F1)

Why would you do this?
One practical reason is due to changes in Blender.
Sometimes you may need to open .blend files in consecutive builds
to update them slowly to the newest versions.
(applies mostly to the particle & animation systems, but not limited to.)