I have an old computer that's running slowly

If you have an old computer which seems to have slowed down over time, you don't necessarily need to replace it. Indeed replacing it presents it's own challenge of how to transfer your settings, files, etc.

Modern operating systems (the software that provides the "friendly interface" for you to use the computer) can consume a lot of memory. That can mean when running several applications, not all applications can fit at the same time and your computer will start to use it's disk to swap in and out bits of memory. The problem is that disk is slow, and therefore this has a big impact on performance.

How can I check how much memory I have?

If you're using Windows, you can check your memory by using the Windows/Start menu (very bottom left of the screen), find "Computer" on the right hand side and use the right mouse button to click "Properties"

You should see a screen like this

Installed memory (RAM) shows the physical amount of memory installed.

4.00GB should be seen as a comfortable minimum. If you have less than this, or notice that your computer's disk light flashes a lot while you're starting applications or switching between them, then you would most likely benefit from installing more memory.

Memory comes as physical sticks of computer chips, and you will need to open the computer to install them.

I notice my computer is just sluggish and it takes ages to start-up

If you have an ageing computer or laptop, you may do well from replacing the disk in your machine to a solid state drive.

Disks historically work as a rotating disk of magnetic tape with a head which moves back and forth across the surface to read and write data, in a very similar way to a stylus across a rotating vinyl record. Although the disk spins many thousands of times a minute, the computer has to wait for the rotation of the disk to access data - especially if it is physically spread over the disk itself.

A solid state drive exists on a computer chip and does not suffer from the need to wait for rotation of the disk. As a result they are many, many times quicker than an old magnetic based drive.

Replacing your existing disk with a solid state drive is, in most cases - the single most effective upgrade you can make to speed up your computer.