The highest CPU the Inspiron 1150 can handle is 2.66 Ghz Pentium IV. Anything higher will overheat. Be sure to clean the heatsink and use some thermal paste on the CPU.
You can but you can't upgrade it much due to its socket. (LGA 755) If you did you would only bump up the clock speeds. I would recommend buying a new motherboard and CPU.
Dell Inspiron 5520 is much better. It has a newer chipset with 3xUSB 3.0 ports, newer Graphics card, Ivy bridge CPU.
The memory upgrade will speed up processes somewhat but it will be hardly noticeable.
Dell laptop
The XPS is made more for gaming and is a far better computer. It may be more expensive than the Inspiron but it comes with extras such as an aftermarket CPU cooler and a case that makes repairs and upgrades easily. The questions is really if you need it or not. If you don't plan on using it for gaming, video editing or other high demand process, you should save the money and get the Inspiron
Because it makes the CPU run hotter
It's actually a function of the CPU cooling fan. If you call Dell, they can send you a quieter model CPU fan.
Your motherboard may need to be changed when your CPU is upgraded.
You will need a new CPU,as well as the booting software
yes you can.
unlikely most laptops CPU are soldered to the board either get a new one or send it back for an upgrade
Sure can....have done so...you may find the Wifi card from one motherboard or graphics chip doesn't plug into the other so make sure you get the graphics chip with the motherboard. The answer is a qualified yes. The 5100 motherboard does fit in the 1100 case and will mount with the same holes. However, you must also replace the power supply, graphics card, CPU, CPU fan and a couple of other parts. So, after having done all this you might as well have started with a new computer.
In general laptops are not easy to upgrade. You MAY be able to add more RAM, but some laptops are sold with the maximum RAM they can handle already installed. You probably cannot upgrade the CPU, but you can't necessarily upgrade the CPU in a desktop without replacing the motherboard.The only upgrade that you can almost certainly make is to increase the size of the hard drive.