Let's say, hypothetically, I have a Laptop running Windows 7 with the newest insert part here (e.g. graphics card, video card, etc). If a new part comes out, hypothetically, would I be able to buy that part specifically and insert it myself (or take it to a store to do it for me)?

With a Laptop, probably not. Normal PC, yes

Upgrading RAM will be the easiest. Just swap sticks and go.

Graphics card CAN be done but it's sooo much harder. You gotta make sure your laptop is capable first, like if it already has dedicated graphics. If so, there are two types, one with the card buried inside, so you gotta disassemble everything to get to it, the other with a cover on the end where you can switch it out. Most will require disassembly. But even when you get past that part, you gotta find a place to buy the new card, which could be a challenge. Newegg doesn't carry any, if I remember from my own search last year.
You're gonna have to ask your laptop manufacturer probably, cuz they seem to all be OEM parts. Then you gotta convince them to sell one to you. What a PITA.

Dunno about upgrading processors. I mean it can be done, but I don't think it will give you as much of an upgrade cuz you'll be limited to the same socket. Steps are gonna require disassembling everything, plus the heatsink. Good luck finding those too. :<

Well....you can always upgrade the battery by just buying a new one

And I think it is possible to upgrade the screen if your laptop model had the option of a larger screen when you bought it. That's still gonna put you at the manufacturer's mercy.

So upgrading IS possible, but it's gonna require a shit-ton of work, probably an hour or more. You'll void the warranty for sure, and it's a lot easier to mess something up while you are at it. Supplies will be much much harder to find, too. It's not like a desktop where you can just open the cover and swap in 5 minutes, it's an operation that'd be the result of desperation.

As much as I know, that would be virtually impossible to accomplish on a laptop. Graphics cards are, most of the time, soldered to the board and they depend on something more than just the chip. So even if you manage to take the graphics chip out and then swap it for a different one, it probably wouldn't even work... Like I said, there is more circuitry needed that is specifically designed for the graphics card, for example the dedicated memory of the graphics card.

However, most custom build laptops such as Compal or Clevo brands don't use the regular laptop graphics cards on the motherboard, they use MXM modules that look like this:


So you will be able to switch graphics cards easily if you get such a laptop... I'll be hard to find this type of technology on an Asus, Toshiba, HP, Acer, Sony and other popular brands though... Most of these brands usually don't build many laptops with this technology.
Try looking for Clevo or Compal, like I said.

Some dells do, but that's true.

I was looking at this article
http://www.pcworld.com/article/14890...hics_card.html

On his it wasn't soldered, just nestled in and screwed, so you might be in luck.

Just noticed you didn't say you already bought one (glanced over the "hypothetically" part :P)
So...

The custom built ones will definitely be swappable, so if you plan on upgrading, GenkiSudo's recs are good.

Although, if you know you'll be having the upgrade bug, it might be easier to buy a more budget laptop and spend the difference on a desktop. Just my opinion, cuz I'm at home mostly, but a lot of people will want to carry their power everywhere.

That article is focused on high-end laptops. The majority of laptops don't use that system. BTW that uses a special dell slot to connect the graphics card. On most of the other brands the graphics card (when interchangeable) will likely use an MXM module or similar.

For more info check out:
http://www.notebookcheck.net/Upgrade...rd.3236.0.html
http://www.notebookcheck.net/Case-St...00.4187.0.html