Unexpected seeming bad performance PC always occurs from a sequence of obvious conditions. Reasons why it occurs from, may depend on hardware and programs. Let's have a look on main reasons of bad performance PC.
Reasons why your computer is slow
Try to remember what have you done when PC is starting slow down. Start task manager by typing 3 buttons simultaneously (Ctrl+Alt+Del).
Look at the list of running processes and find those that have the largest percentage of using CP.
Make sure you are using only one antivirus and its virus definitions are updated. Using some antiviruses simultaneously is not very good practice because its performance may not be enough to find bad software. You should start scanning all of system folders and directories for viruses.
Check your Laptop or PC for getting warm. In case of using the laptop, it is enough to touch the bottom cover. It must not be very hot. Also the evidence of overheating may be work of fans on high speed continuously.
If you find some of those symptoms, probably your device is very begrimed with dust inside. So you should clear your device thoroughly. To get a great effect, you should dismount the bottom cover carefully (in many cases it can be done very easily or you can find on YouTube a lot of videos about disassembling your model) and by using special tools, blow off dust from all dust-filled areas.
Also it is very often can occur problem of dysfunction in functionality HDD. It may has some damaged sectors because of this the system runs slowly. The HDD must be tested for errors by special software, "Victoria" for example.
If test results show any errors the HDD must be repaired or replaced to other HDD.
If these advices are not helpful or you have specific questions, please try to describe the problem more explicitly and do not hesitate to contact us, we will help you without fail.