HP Desktop Computers
Hewlett Packard has been in the PC building business for quite a few years (and in the general "high tech" industry for many more before that). Their "Pavailion" series of desktop PC's have been staples in retail stores for a long time. They also provide their "Series 2000", "Series 5000" and "Series 7000" to businesses.
Compaq was a major player in PC's for awhile, but eventually lost much of their market share and were eventually absorbed by HP.
