How practical is it to use a raspberry pi for a POS system? I'm in a small country where bring in a large quantity of POS system will cost too much. Was wondering if i can replace the current motherboard system of the outdated POS with a Raspberry pi and install windows xp.
By POS I assume you mean Point of Sale System. There's no reason that you can't use the Raspberry Pi as a point of sale system, but you'd probably need to write such system yourself.
While it is a full fledged computer, there are some fundamental differences between the RPi and a standard desktop computer. The primary difference that will cause you problems is the architecture type. I went into some more detail about that on our blog.
In summary, programs compiled for a standard desktop or server system won't work on the RPi. You'll need a binary specifically compiled for the it. If you can find an open source system that you can compile yourself, or there's one in the repositories already, you're golden.
You certainly can use the RPI as a POS, and there are projects like Odoo (an open source ERP system) that do exactly that.
With the 7'' touch screen that was designed for the RPI, you could even have a nice touch screen interface for your POS at the cost of ~USD 120/seat for the RPI with the screen.
However, if your POS software is Windows only, than you are unlikely to benefit from the RPI for this deployment.
Try IotPOS: https://github.com/hiramvillarreal/iotpos
I am the developer and have been using it more than 2 years at grocery stores and restaurants.
ViewTouch offers Point of Sale on the Raspberry Pi under the GPL, also known as the Free Software License. Visit http://www.viewtouch.com for all the details.