Dear knnkalose,
When you want to buy a specific product from the company you raise purchase order. Examples for raising purchase order are purchase of boiler, DG set, Xerox machine etc. In the PO you need to mention equipment specifications, delivery address, installation charges if any, payment terms etc. In addition to this if the equipment needs to be transported inland or overseas, you also need to mention INCO Terms.
When you give contract to some service provider to provide some services, you need to raise work order. Examples for raising work order are installation of plumbing system, refurbishing marble flooring, hiring training services of training professional and so on. In the work order you need to mention type of services, labour charges, material to be used, etc.
In few companies, purchase order is issued even when services are hired. This is because these companies are ISO certified and staffs have to use certain forms and only and no forms are to be created on their own.
In your case for the purchase and installation of software only you need to raise purchase order. However, if you want support services from that software company beyond 'x' time period, you need to raise work order.
Hope this clarification satisfies your requirement.
Thanks,
Dinesh V Divekar
.