You can make the order prefix separate from the database... if ALL orders in your store begin with AIW- then the way I would do it:
1. Determine where order numbers are displayed.
2. Change the template that dispalys order numbers.
For example - in /skin1/main/orders_list.tpl
find:
Code:
<td><a href="order.php?orderid={$orders[oid].orderid}">#{$orders[oid].orderid}</a></td>
instead of
#{$orders[oid].orderid} - you want it to be:
#AIW-{$orders[oid].orderid}
yes?
Find all the other places that an order # is displayed (use webmaster mode) and go to town.
That's the "easy" way. The hard way will be to create a table and append alpha characters to the table and I wouldn't know where to start. Beyond me. This makes your order number a simple display/template fix, not the underlying order number.
Will this work?