Occasionally we run into very old versions of Sage 100. These are typically defined as any version 3.x.
Thankfully, you can upgrade all of your existing data without no re-keying. Here’s how.
First, I recommend you start off at version 3.71 or higher. If you are on an earlier version you should upgrade to 3.71. I found it was sometimes possible to install 3.71 on top of ( aka in place ) the older release. If you install over the prior Sage version be certain to take a full backup first.
From 3.71 you should be able to migrate directly to Sage 100 2017. If you try to go higher than this you may receive an error suggesting that you migrate to 4.5 PU8.
From Sage 100 2017 you can migrate to the latest version of Sage 100.
Be sure you make backups of your original MAS 90 data and program files before you begin.
Finding source files for each of these versions is a bit of a project so you may want to enlist the help of your Sage partner.