i) run a full virus & spyware scan (windows 10 has one pre-installed, run Windows Security in your programs list; else get free Antivirus / Spyware software from either www.avast.com or www.avg.com).
(NB it is important that you only have one Antivirus solution installed, and that it has been updated prior to a scan).
ii) Error Check the hard drive (right click on C:drive, select Properties, select tools, select Error Checking, click Check)
iii) Download the free version of CCleaner from www.ccleaner.com/ - once installed, (a) Run the EasyClean function, then (b) click on Registry, Scan For Issues, then Fix Selected Issues, (c) Click on Tools, Uninstall and then uninstall any software you don't use any more.
iv) Defragment the hard drive by either (a) Running windows Defragment utility (right click on C:drive, select Properties, select tools, select Optimise), OR (b) you can install the free version of Defraggler from www.ccleaner.com/defraggler and then run this (nb this option will be quicker).
v) Optional - Go to System Tools in your Programs list, Right Click on Command Prompt, Click on Run as Administrator. When the Black window appears enter the command "sfc /scannow" (without the quatation marks), this opens and runs the Windows System File Checker tool, which Checks & Repairs (if necessary), all the Protected System Files.
Hope this helps.
P.S. The other way to speed up an old laptop is by (i) adding more RAM & (ii) by replacing the old hard disk with a SSD (Solid State Drive). If you want to explore either of these options, then run the free system scan at uk.crucial.com/
PPS the final way to get better use from an old laptop is to replace Windows with a light, user friendly version of linux. I'd recommend zorinos.com/ which aims to be as much like Windows as possible (nb make sure you download the Lite version for an old computer, also make sure you download the right version 32 or 64 bit - (when you run CCleaner (as above) at the very top of the page it will say whether your system is a 32bit or a 64 bit machine).
If your machine is Windows 7 the above will be a very good idea as Microsoft are going to stop issuing Windows 7 updates in the New Year, so your computer would thereafter become vulnerable if you continued to use Windows 7.
Sorry, turned into a bit of an essay - I'm a bit of a geek!