How to buy, setup (hardware), build, choose, or start with linux computers/components
# Step 1. Find a distro
For newbies, use the most popular linux distro for maximum support.
If you like a particular look and feel of a distro, just customize the popular distro according to the look and feel of your choice. Trust me, don't waste your time on this!
Google for "distro rank"

32 bit or 64 bit?
quote"... installing a 32 bit OS on a 64 bit machine is generally easier than installing the 64 bit version. 64 bit drivers are not available for a lot of hardware. A lot of software is only available in the 32 bit version. This can lead to problems when you need to mix and match 32 and 64 bit software. For example: running a 64 bit web browser with 32 bit plugins like Flashplayer. " end of quote

# Step 2. Find a motherboard
Chances are that your local computer shop tell will you which motherboards are linux compatible.

or Google for "linux computer <your city>"

Or Go to your distro's hardware store...
Or Go to -> Computers & Networking -> Computer Components -> Motherboards
Under the search field, check the box of "Include title and description",
search for "linux",

or search "linux" under -> Computers & Networking -> PC Desktops or PC Laptops & Netbooks

Check the compatibility list
Google for "<distro name>" with "hardware compatibility list"
Google for "<distro name>" with "motherboard" or "mainboard"

if you have time for further research...
Google for "linux hardware compatibility list", for example:

... Most motherboards are Linux compatible. For the different chipsets, there is usually a driver at Linux kernel...

# Step 3. Find accessories...
Hard disks, monitors, optical drives, keyboards, and mice are generally all linux compatible.
But for the following devices, make sure you check linux compatibility lists first, before buying them! wireless adapters, printers, microphones, webcams, camcorders, cameras, video cards, sound cards, ...

Ebay is a great source for compatible hardwares, too!> Computers & Networking->
check the box "Include title and description",
search for "linux", then click on the components on the left
or search for "linux wireless adapter" or "linux webcam"

Enjoy it! =)