While this is only one experience, my 2003 G4 laptop runs great with no slowdown. I haven't needed another computer since. Whereas I can't even count on my hands how many times my roommates Dells have been serviced.
Go out and get Call of Duty 4 or any newer title and try to play it on that 2003 laptop of yours and then get back to me...
And as far as the Dell is concerned, I'm not going to stick up for them, because they are only one of several mainline computer manufacturers, but a lot of people don't take care of their computers...
If you go buy a Honda Civic, or any other reliable car, and don't change the oil on it, or replace the breaks, eventually, bad sh*t is going to happen.....
This is the same type of stuff that happens to people that don't protect/take care of their PCs.... A lot of people don't know/care enough to run a weekly spyware scan, to delete their temporary internet files/cookies, and to keep a an anti-virus and firewall running constantly... As someone that has 'serviced' computers for a living before, this is the root of 75%+ of the problems that people experienced.
Another huge problem is people not knowing what they are installing on their computer..... I went to one ladies house that was complaining that her computer was running 'really slow'. Come to find out, she had some 30+ programs in her tray that were set to run when her computer started up; just eating away at her available memory.... These are all things she installed over the years without paying attention to the 'start this when windows starts' box. After removing all of these parasitic applications and defragmenting her hard drive (something people should do as well), it ran like new.
This is the easy type of stuff that people neglect to do over time that really leads to them thinking their computer is 'has a virus' or is 'out of date'.
Very rarely is component failure the issue when people need 'servicing'. It certainly happens when a computer isn't shipped properly and is more common in laptops, but it is rare.