If your notebook is old of some years and maybe has slow down you can update it without you need to buy a new one.
Hardware upgrade:
to make the notebook more powerful you can change the actual traditional hard disk with the more performant SSD, now they are more cheap.
The gain in terms of speed will be very clear.
If you still want continue to use traditional hard disk (for data storage, downloads, etc…) you can use a cool accessory like Silverstone TS06 so you can place in the DVD box and the dvd device will be transformed as an external USB device.
Another high suggested upgrade it’s about RAM.
Generally notebooks are provided with 4gb, if you put double and high quality (eg. Corsair, Kingston, ecc…) the notebook will speed up a lot.
Lastly, especially if you haven’t never done, it’s suggested to disassemble it and do a deep cleaning, the dust is an enemy!
Software update:
If the notebook runs for example Windows 7 or Vista OS (in this case the update is even more suggested) you can update by installing the latest Windows OS.
Please verify the drivers availibility before proceed, there are also some free programs that allows to update them easily.