Restart your laptop and, before you do anything else, open the Task Manager. (Right-click on a blank space on the bar at the bottom of your screen and select 'Task Manager' or press Ctrl, Alt & Delete together). Click on the 'Processes' tab. Maximise the window the full size, then minimise it down to the bottom of your screen.
The reason for doing that is that you'll need to examine that processes page when things start going slowly (by simply clicking the Task Manager box at the bottom of your screen) but starting Task Manager
after problems have started to occur can take forever.!
As soon as you start experiencing problems, maximise the task manager window and look down the 'CPU' column. Normally everything there should show a very low figure, such as '00'or '04'. The only exception should be 'System Idle Process' which should typically be around (say) '95' or '98'.
If anything other than System Idle Process is showing a high figure, that will be the cause of your problem. (i.e. something will be hogging all the processing power of your computer. Tell us what it is if you don't know how to deal with it).
If everything under the CPU column appears to be normal, look down the 'Mem Usage' column. There are two things there which should set alarm bells ringing. Firstly, any process with a really high figure is clearly hogging nearly all of your computer's memory. Secondly, any figure which is constantly changing (even though it's fairly low) suggests that a program is stuck in a loop or otherwise failing to run properly. 'MsMpEng.exe' often exhibits such behaviour for example. It's the part of Microsoft Security Essentials which updates the data; it sometime seems to 'get stuck'. As before, if you spot something odd (but don't know what to do about it) let us know what it is.
Something else you can try is to run Msconfig (by typing 'msconfig' into the box which appears from Start > Run) and click on the Startup tab to see which programs run automatically when you start your computer. (If there's anything you don't actually need, click to remove its tick, then click 'Apply' & 'OK' before restarting your computer and putting a tick where it says 'Don't show this message again' in the warning box which will appear.
Further, check to see if any malware has found its way onto your computer. Download, install and run the free version of Malwarebyte's Anti-Malware:
http://www.malwarebytes.org/products/malwarebytes_free/
(NB: During the installation process, remove the tick that installs a trial version of the 'PRO' program).
Chris