Having been burned in the past, my take on this issue is...
Basically, the sale of your expertize is a contractural agreement -- you agree to do the work; they agree to pay. Unless you have a proven and reliable customer, in the future protect your self...
-- Get a Purchase Order number from them. The PO is their agreement to pay you for their services. This is your proof that they have agreed to do the work.
-- Issue them a Work Order number stating exactly what you are going to do. There are those out there with less scruples that will claim they are not paying you becasue you did not do the work.
-- Get the customer to sign the work order.
-- Document that the program is an evaluation copy only, valid for 30 days lets say, subject to payment. After the evaluation period, use of the program is null and void type of thing. This is a mechanism that may allow you to disable the program in a more ethical manner.
-- When the work is complete, get the customer to sign off on the work order indicating that services have been delivered as requested.
Now you have...
- An agreement to pay you
- An agreement to do the work
- Proof that the work was done
The aforementioned process and supporting documentation should be reviewed under go a legal review. Laws and bylaws will differ depending on the country and state or provence.
And for your existing deilema, yes, go the lawyer route first for trying to receive payment before going through small claims. Cheaper, and will help your cause if and when you go to court. "I did this, this and this". Whereas, the customer, if they decide to show for the court appearance, may look a little silly if they have no supporting documentation.
As I understand it, one of the biggest problems with small claims court is that one of the parties does not show, and ignores subsequent action.
You may also consider releasing your claim to a creditor. They get a hefty cut, but then the vender will get black marked as a credit risk if they do not pay. This may haunt them later if they try to secure a loan, or if supplier runs a credit check.