First off, I am not responsible if this messes your data up. This worked for us and may or may not work for you. Use are your own risk.
Current version we had installed was Mas90 4.20 and we needed to move that to a new computer. We had an update that wasn't installed yet.
First thing, Navigate to where mas90 is installed. Our was installed in c:\Program Files\Sage Software\Mas90\Version4\Mas90\...
Copy the Mas90 folder to another location because that is what we will need to do the migration.
If you haven't installed it yet, install 4.40.
Once it is installed open it and look at the left hand window pane under the Tasks Tab. Click Modules -> Library Master -> Utilities -> Parallel Migration
The Parallel Migration Wizard will load and ask you to click ok to close Mas90. Click ok. Click Browse and select the Mas90 folder we copied earlier. Click Ok and Click Next.
Click Yes so you can migrate any companies that already exist in the new installation. Most likely this shouldn't be the case. You should have zero companies if it is a fresh install. Click Next. At this point select all the companies you want to migrate. Click Next. Verify everything looks right and click next. The wizard will now migrate all the companies you selected. Click Finish when you are done.
Open up Mas90 and select your company. All the companies you migrated should be located in there.
The next step is to convert the companies from version 4.20 to 4.40. In the left hand window pane, under the tasks tab, select Modules -> Library Master -> Main-> Company Maintenance. Type the company code and hit enter. It should show all the data associated with it below. Now click the convert button. A warning will then let you know that "Data entry files may be cleared. Back up your data before converting". Make sure you have a copy of that original mas90 folder .
Now we didn't try this but there is a box that will convert ALL companies. If you have more than one, that should save you time. Like I said we didn't use it so I don't know for sure. Click Proceed. Click Ok when its done.
If it worked correctly you will now see the the Activated Modules Data Level will say 4.40. Your Company was successfully migrated.
Note: We originally tried to load 4.20 on Windows 7 and it required Microsoft Data Access Components (MDAC). I was unsuccessful to get 4.20 to work. Maybe I missed something but I just wanted to make the note that 4.20 was originally running on Windows XP and were unsuccessful on getting it working on Windows 7. 4.40 installed smoothly on Windows 7 without any problems.
Here is a good website about Mas90 Link