As for desktop computers, I prefer to assemble them myself on my specifical needs (i.e. my workstation), or with used parts I get for free (for office computers where high performance is not substantial).
I'm not very prepared on laptop computers, but i have an HP Pavilion and a retailer I worked with told me that HP is one of the best brands for reliability and assistance. I voted Toshiba too, because it's another high-performance brand.
Hmm... I will take this from a laptop perspective, as they are mostly bought as whole units with a brand name. I picked Toshiba, as I have a few Toshiba Portegé laptops, And they rock! 11" weight less than 2KG. Can't get better than that?
Also, IBM Lenevos, They are of a great build. I don't personally own one (wishing too though!) but I have used many other peoples laptops.
As for desktops... Well normally I go for AMD processors, always have done, But I am likely to swtich to the Core Duo whatever for my next machine. With an ATI graphics card... I normally get ATI, but recently I am using my first nVidia. Its done well so far, But I miss my ATI .
As for motherboards... Anything will do, as long as its upto my required spec and doesn't have a VIA chipset. Seriously, how are VIA still in business? I never had bad troubles from them. And maybe for my next purchase, try and get as many PCIe slots. Not all for graphic cards. But I might want to add some speedy Stuff in there. Like a 10GbEth Card when it comes around ;-) or some SATA3 raid controller.
Ram, erm... some generic brand name. Never go for the cheapst stuff... Guranteed to be dogey or dead stuff. Powersupply, again, not the cheapest but a brand name generic brandname for a decent price. Not pickey really.
2.) Dell / HP (tied)
1.) Dell / HP (tied)
I absolutely hate Gateway as a company, and their machines are usually made of dirt. I don't really like VAIOs either, not because they're a bad company (Sony), but because from my experiences their internals are not very reliable, namely their RAM and Hard Drives.
I Have a Gateway i don't know what possessed me to buy it though. i could have gone with a dell and probably saved some money. I Built my desktop though, and i have to say i would do it again, its nice to know whats in it and how it works, easier to fix if anything goes wrong.