If you are windows user then the first thing I can suggest you that on search panel type %temp% after typing this you can see a lot of temporary files and these are responsible for your system's slow speed.
If still, your system is working slowly then I suggest you that you should run a disk clean up. This process can clean up your hundreds of megabytes by deleting temporary files, unnecessary system files, and emptying your recycling bin. What you have to do is Click on My computer, right-click Hard Drive, then click Properties. Click Disc Cleanup.
If performing above steps still your system speed is slow then I think its time to upgrade your RAM and processor.