Not hard, but limited. Things that you can upgrade are RAM and hard drives. Everything else is integrated or require more work and knowledge to replace. You get what you pay, pretty much.
well yeah, i was looking at a nice HP pavilliion with integrated lan and dvdburner and evrything, but its only a 40 gb hdd, so i figure i wanna swap that out, because the one with 100 gb is a lot more money and has useless crap i neither need nor want