I've got 2 year old Dell Inspiron 1521, its fine for what I use it for but I recently got Call of Duty Modern Warfare and the processor and gfx card understandably aren't up to the task.
The specs are:
AMD Turion 64 X2 Mobile TL-50 Dual Core 1.6Ghz (I think)
Gfx is a ATI Radeon Xpress 1270
I don't really want to splash out on an entirely new laptop as there is nothing wrong with this one except its a bit slow.
What would be compatible with my laptop upgrade wise? I was thinking of buying a higher spec Inspiron (maybe with a broken screen or faulty so its cheaper) and using it as a donor to migrate a the motherboard/cpu/gfx over to my laptop? Im fairly competent with the practical side, I used to build my own desktops so that wouldn't be a problem.
99% of laptops are a dead-end when it comes to upgrades... why do you think yours is in that 1%? Building desktops and laptops are two entirely different animals. Don't really think you're going to have any cost-effective options... maybe you're a good candidate for a $500-$600 budget DESKTOP build.
I have had the misfortune of replacing a laptop's screen once and I'd describe it as the most painful hardware swap in my life. Nearly 30 screws and ~2 hours of my life down the drain... and the ONLY reason I did it was the replacement part was provided to me at no cost. Had it cost money I would have pulled the memory and drives out and tossed the laptop.
I hope someone here has a more optimistic outlook on your problem, but I wouldn't count on it.
Your GPU is an older Radeon when they used to build them into the motherboards. The chances you'll be able to upgrade that to something worth the time and money are about 1 in 10 million. Notebooks are meant to be minorly upgraded only. Replacing CPUs and GPUs and motherboards with different models can run you into dozens of problems, because none of them are standardized. Working on notebooks is worlds away from building a desktop, where everything conforms to standards.
Generally speaking... memory and hard drives are about all you can expect to upgrade on a typical laptop. Sometimes you can get away with upgrading the processor, but that really isn't a guarantee. In most cases you're stuck with the GPU.