The first step in building your custom computer is the case.  The case is the outer box in which we will install the workings of the computer.  There are many factors in deciding which case you require for your computer. 

• size from small cube designs to large towers to rack mount cases 
• prices start @ less than $15.00 to well over $1000.00
• color just about every color is out there just need to look
• design basic to bizarre and beyond
• steel, aluminum, plastic, and other materials
• number of slots available for expansion (hard drives,cdrom drives)
• built in accessories (card readers, front usb ports, front sound ports)

Three places to check out the choices for your case decision are price-watch and Check it out @ Geeks.com and Newegg.com has all your computer and electronic needs!
There are plenty of other places to search for a case for your custom build just type computer case in Google search  and you will find them.  Don’t try to get ahead and try to buy the case without having the rest of the selections made as you might be able to save some postage by purchasing multiple items from the same vendor.  For now just make a note of the case choice and record any model number you can find so that when you are ready to begin purchasing the items you have them handy.