Use Memtest86 and badblocks to test a computer

What I use to test if a machine works, is use Memtest86. Run for a few hours and see what it comes up with. If it comes up clean, then its usuable. Else send it back. Make a temporary floppy disk for the purpose of testing. The “badblocks” & “smartmontools” utilities are great for testing hard disks and “memtest86” effective at testing memory. The former is included with many distributions while the latter is available with some disaster recovery kits or from http://www.memtest86.com/