I have been working in IT for a few years now and I have worked on all the models of computers out there. Here is my ranking of some of the top companies generally speaking.
# 10. DELL - In a word garbage, don't waste your money. Extremly cheap components and some of the worst tech support. Why do they sell so many machines - the power of advertising.
#9. Alienware - Extremly overpriced and prone to failure.
#8. E-Machines - Inexpensive machines, and you get what you pay for.
#7. Acer - Decent enough midgrade machines but don't get your expectations up.
#6. Sony - Too expensive.
#5. Gateway - Good starter computer, but be sure to backup often.
#4. Compaq - Since the merger with HP they are much better than they used to be.
#3. Toshiba - Good machines, very durable.
#2. IBM/Lenevo - Since they invented the PC no surprise. Their machines last forever.
#1. HP - My personal favorite. Great tech support, tough machines, and very dependable.