I have found lots of payment gateway, now the problem is what script that enable the buyer to pay first before downloading the software.

I would like to sell premade logos on my site.

Any free or paid?

This is not hard.

example: I'm using 2CO, and I customize the item details to put "approval url" --> this is where the customer is directed after a successful payment (Hint: this can be your download page).

If you are looking for PHP - check out www.cmsmerchant.com

Girg by mindsoft is good it allows downloads of products once they have been paid for (paypal only i think)

Thanks for your reply.

By the way i found a site that do what i've mentioned: www.payloadz.com