Hello Edgurr:
In your situation, you have 3 choices:

1) If you understand Tech Support's explanation, have some technical skills and LOTS of time and patience, you will eventually be able to print onto a 7" dot matrix cheque.

2) You can pay your Adagio consultant to do the sweating and cursing to make the cheque printing work on the dot matrix.

3) Switch to laser-printed cheques. This is the option that will cause you the least frustration and almost always be the cheapest (given that your time has a cost to it).

Some firms have valid reasons for using dot matrix cheques. However the "I have 3 boxes in the cupboard" rationale is not one of them. People have a strange emotional attachment to their stock of cheques. What's a box of cheques worth? 100.00? You will spend much more than that getting dot matrix cheques to work with any Windows-based accounting system like Adagio.