You have to know that this Laptop is very old, so don't espect too much, but there are some Tricks you can do:
1. Of course checking for any viruses
2. Try defragmentate your harddrive
3. Uninstall unwanted/unused programmes, check your settings and the Autostart, if you are useing Windows
4. If that doesn't help you can Try reinstalling the operating systhem/swiching to a more siuted one (for "modern" use i would suggest some kind of linux) or opening the Laptop and cleaning the parts for better cooling (and replacing the thermal paste)