I am hoping that I will be receiving an old Alienware desktop tomorrow. The first thing first will be to decide what generation it is and what the hardware already is. If it is a Core 2 or newer, with PCI-Express, which a Core 2 motherboard should have, I will be popping in my AMD Radeon 7850 and seeing what it can do. Otherwise, the fun begins.
Check powersupply rating and revision for suitability with new components.
Look at cooling and ensure that it is up to the task, if not, what can be done, to rectify the situation.
Research Components: Motherboard, CPU, RAM, SSD, Hard Disk, DVD/BluRay?