how to find out if a system has a pirated OSX.

[sswats]

When buying a used mac how can you tell if a system has a copied OSX?

Secondly I work in PC repairs and we want to expand to basic Mac stuff. So regarding upgrading Tiger systems to snow leopard. It doesn't seem to state it on Apple site, but with a clean install they should only need to buy the £30 Snow leopard right without needing to install leopard first, right?

Going back to the dodgy copy question, I am competing with a more dodgy market stall not too far away willing to use copied versions of snow leopard (and windows) What reasons do i give to the customer to avoid copies (apart from the moral argument which often falls on deaf ears). eg with windows, there will be a lack of security updates leaving system open to virus' or the fact that they may eventually get blocked by MS.
So whats the argument for using only legitimate copies of OSX?

 

[sswats]

Its a computer market with a few people. I don't know which one specifically does it. just customer came in for a quote about upgrading her Tiger to Snow leopard, I told her software alone is £132. She then told me someone in the market offered to do it all for £45.

But we're far enough away towards the richer part of the area to not need to compete directly. And you mac people tend to like giving money to apple so its usually not too hard to convince them to be legit.