I normally don't write "short" articles, as I usually have so much information to give! But this one should be rather quick in comparison. I love working on my laptops, but I think even people who aren't afraid to do so can get lost on what preliminary measures to take when upgrading.
Maybe you have a decent laptop, but it's running a very slow dual-core CPU. If you want to upgrade it you need to know a few things. The first is what family of mobile processors it belongs to. You can usually find your processor and its respective family on Wikipedia lists. Once you find your processor that same list on Wiki should show you other CPU's from that family. You can see what is better than your CPU and start looking for your replacement.
Sometimes, a family might use the same pin configuration as a predecessor or successor, meaning that you may be able to find and use a newer CPU family. However, I would say this is seldom the case.
On that same Wiki list of CPU's, it should denote how many watts your CPU is. This is VERY important. A normal desktop can have its power supply upgraded, a laptop cannot (without major "hacking"). The most that you might be able to do is find a corresponding laptop power adapter that supplies more wattage than your stock laptop power adapter.
The reason this is significant is because upgrading a CPU (or a graphics card) can increase maximum watts needed to power your laptop. If your laptop's CPU only uses 15 watts, this may mean you have little to no extra wattage available from the laptop to upgrade. Maybe a CPU that is 25 watts will work. But maybe a 35-watt CPU will not. Maybe none of them will work, maybe both of them will.
This really becomes a guessing game unless you can break down all the individual components and how much they use. Components like a hard drive, RAM, and an optical drive may not use much, but they do add up. The bottom-line is moving out of the stock CPU's watt range is a risk.
Helpful Tip #1
If your laptop was a laptop that had different CPU options, you can check the manufacturer's page (or elsewhere) and see what options were available. There could be high-end option, in which case you can investigate to see how much watts that CPU can use to give you an idea of what CPU you can upgrade to.
If your laptop didn't have different CPU options, you can explore forums for others with the same or a similar model to find out wattage information.
By far the cheapest bang-for-your-buck upgrade that can be done is RAM. It is comparable to upgrading the exhaust system of a car. RAM can be great for multitasking, virtualization software, special effects software, and much more. The only limitation is usually whatever the manufacturer says it is... or is it?
Most laptops will have specifications that state how much RAM a laptop not only comes with, but how much it can be upgraded to. From what I have found, this can be wrong.
For example, a laptop may say that it can only support up to 8GB of RAM. However, what is not mentioned is how much can the CPU support? If you look up the CPU you will find a specification for the max amount of RAM it can see and handle, and at what speeds. Let's pretend that the laptop has a CPU that can handle up to 16GB of RAM. This means there is a very good chance you upgrade the RAM to 16GB worth.
Note: Higher speed RAM than what your laptop can handle should still work, as the system should slow it down to make it work.
Helpful Tip #2
Just because your CPU can support more RAM doesn't mean your motherboard will. While I have never come across this situation, I have read posts from users where it does. The best thing you can do, if you're willing to take the risk, is buy the amount of RAM you want to upgrade to, and make sure it is a quality brand. I have heard that may make a difference. I have only tried Corsair "Value" RAM with success.
Graphic cards can be a little trickier. Some laptops don't use graphic cards at all, so if you have one of those your out-of-luck. (Unless you do an external graphic cards, but the cost vs. power increase will likely not be worth it.) If you do have a graphics card slot, then you can very likely upgrade it.
Many of the same tricks and requirements for upgrading a CPU apply here. Including making sure that your laptop power adapter supplies enough wattage, and if you will go out of the stock graphic card watt range.
Helpful Tip #3
If you have an older laptop and wish to put in a newer graphics card, there will normally be no native support for your laptop. But don't fret, you can often do a INF mod and get your laptop to recognize the graphics card.
I wanted to remind anyone reading this that your absolute cheapest upgrade will be a laptop power adapter. Yet, this is only a complementary upgrade if you are pushing for higher watts with a better CPU or graphics card. If you stay within the watts of what you already have, this purchase would be completely unnecessary.
I have actually had to do everything mentioned above between two different laptops. The first was an Alienware M17x R2 laptop. A huge laptop (heavy as ****!), with a 900p screen, Crossfire ATI 5870M, and I believe 8GB of DDR3 RAM. The second was recent and for a Sony VAIO VPCSB25FG.
I purchased the M17x second-hand off of a forum. It was fairly cheap and I wanted something I could use for video editing and whatnot when not at home. It came with a cheap CPU that I upgraded to an i7-920XM. This was definitely a wattage increase. I also upgraded the Crossfire setup to a single GTX 680M. Another wattage increase. And because my laptop wasn't made to officially support that graphic card I had to perform an INF mod to NVIDIA drivers.
There is no higher laptop adapter for this model, but from my research, this combination would work. There is a supposed modification to combining two laptop adapters, but it seems that it was a flawed approach. And because of the amount of power the above hardware combination uses, there could be problems between overclocking both items as one would throttle the other.
I did not experience too many problems, but enough to be frustrating. I had to download ThrottleStop to prevent the 920XM from running full speed on start-up. And sometime I cannot boot into Windows 7 without first having the adapter unplugged initially. What's worse, is for no reason, sometimes that little trick will reverse itself where it must be plugged in the entire time of booting.
I also upgraded the RAM to 16GB. I checked on forums and saw that many people were able to accomplish this. I checked the Intel site and it stated the 920XM could handle 16GB. One weird note is that since that time Intel has changed the official specification webpage to state it can only support 8GB. The only way you can know it works with 16GB is if you dig through the technical documentation as it was still there last I checked...
And no, just because Intel changed it didn't make my laptop suddenly stop working!
The Sony VAIO I have only performed a RAM upgrade. I want to perform a CPU upgrade, but I will wait on that. The official webpage specifications for this laptop states a maximum of 6GB of RAM. Which I thought weird since you can't get 2x3GB sets, and laptops only come with two RAM slots.
On further inspection, apparently this series of Sony laptops have 2GB SOLDERED into the motherboard! Great to always have RAM... unless it dies! Anyways, now it makes since that you would be forced to buy a 4GB single RAM stick, which would bring the total to 6GB.
Anyways, I put in a 8GB RAM stick and booted the laptop. It gave no issues whatsoever, and recognized the 10GB of RAM.
Don't trust what the manufacturer's specification are. They might have some validity, but as I have explained, this doesn't seem to be the case for the most part. Many argue that those are just theoretical specs as companies cannot predict what hardware will come out in the future. I believe they just want to force us into buying something "better"; a good trick on getting more money and return customers.
So, if you don't think you can upgrade a laptop, think again! Unless you have already done what I have written, you very likely can.