D1

Security virus protection and/or firewalls.
Firewalls are used to stop unwanted visitors from accessing the software on your computer. Virus protection software can stop viruses and Trojans from infecting your computer. It will also remove any software codes that have already infected your computer. 
This increases computer performance and stops it from dropping as a result of viruses etc.

Clean up tools for removal of cookies and/or Internet history and/or defragmentation. 

Defragmentation is the process of reducing the fragmentation on the computer hard drive.
Clearing your permanently filed cookies will make your computer run faster, and eliminate the link between you and the websites you frequent. Cookies are small files that websites store on your computer to remember your account information, log in and password.
Defragging your computer will delete files left behind from other deleted files, allowing the computer to run a lot faster and smoother.
This improves computer performance as it creates more space for new information and memory.

Drive formatting.
Drive formatting is when you erase all the data on your computer leaving only the core software that comes with the operating system. The computer will be in the same state as it was when it was new and unused. It would be very important to back up any information you need.
The computers performance will be improved more by hardware adjustments rather than software adjustments.