Even with the most sophisticated hardware and software, you need to perform routine maintenance to keep everything working optimally. For regular home use, once a month is sufficient. For heavily used computers, performing these steps weekly is recommended.
Defragment your hard disk drive to keep it in peak condition.
Files and applications on your computer’s hard disk drive are not always stored together as one unit, but are often divided into smaller units and scattered around the hard disk. This is caused by normal use.
On a fragmented hard disk, a computer has to work harder to gather all of the small units to perform the commands you give it; this slows down its ability to access files and run applications. Running Disk Defragmenter helps by putting all like files and applications into contiguous groups so the computer can access them quickly.
If you use your computer a lot, it’s a good idea to run Disk Defragmenter on a regular basis. It’s also a good idea to run Disk Defragmenter after you install a lot of applications to enable them to run at top speed.
Remove unwanted softwares. Only install which you require more and finally use disk cleanup applications like CCleaner which cleans temporary files, browser history, windows registry etc.
The end result is simple.. your system is finetuned now. It will work as new one.