I don't know about the QLD stores, but MSYs customer service in NSW is terrible.
I would go to www.umart.com.au. They are QLD based and have pretty good prices as well as good customer service.
The umart systems have this note:
Purchase a copy of Windows 7 or 8 32bit/64bit and have it installed for free!
It just means Windows is not included in the price, but you can add it to your cart as well and they will install it.
Aside from the computer packages they offer, they can also assemble any custom parts list.
You can get assistance on these forums with parts to use.