Over a period of time a computer can become dirty both literally and figuratively. The cooling fans in the computer draw air into the case to keep the internal components cool. Whatever is in the air will be drawn in too. Common contaminants include dust and fibres from new carpets, and animal hairs. Tobacco smoke can be a particular problem because it is quite sticky. These contaminants can coat the internal surfaces and clog up heatsinks and cooling fans, causing the machine to get too hot and making the fans spin faster, making it noisy.
Your software can also create problems over time. Temporary files get created and not removed, some of which can be quite big. Windows itself creates lots of log files that may not be needed, and software you thought you had removed may also have left bits of data behind. These problems can lead to your computer being slower and noisier than necessary, and overheating can shorten its working life or even cause it to crash.
How regularly your computer needs a health check depends on how you use it. Feel free to contact us for advice.