When it comes to lap tops, sometimes... It just matters if they give you the doors to get into each spot. Sure you can send it out and have the case cracked open by some computer tec (or if you have the nerve, you can do it).
Some laptops.
Video card, Maybe, if there is access. (but lots of money for one compared to desktop) or split the case.
Ram... Yes, I would say almost all have access to the ram
CPU... Split the case.
HD... Yes/No. Main drive, split the case. BUT extra drive added to a drive bay.
By the looks of the link you given, what you see is what you get, maybe you can update it later like I have talked about before, no option with that model.
IMO if you want to pick what goes into your lap top, go to DELL and as much as it hurts me to say it, you would be much better off with DELL then HP.
Now with that said, what do you want it for? If you want to play games like COD4, forget it, it would take around a $2,000 model of "something" to get the lap top close to running newer games.
No matter what you pick, nothing is ever better then a desk top for the "same" cost as a lap top.