|Since you have provided very little information, here are some idea's.|
A pc slow down can be caused by a few things.
1) Check to see how full is your hard drive, anymore than 90-100% full is bad?
2) Check how many programs run from startup and continue running even when not used?
3) How much RAM do you have?
4) A virus.
Lets try eliminating viruses, a quick scan with Malwarebytes first.
Download and run Malwarebytes from this link:
If anything is found, include the log in your next reply please.
Please reply and let us know if our help worked.