Hi, Can you say if you are using a desktop pc (tower & separate keyboard) or a laptop with extra mouse & keyboard. Plus, are the keyboard & mouse wired to the pc, or wireless?
If it's a 'normal' type of set-up, I.e. no special keyboard drivers required, then faults like this could be as straightforward as the pc needing a 'defrag' or two.
The Windows defrag program is ok, if a bit slow, I tend to use the free & effective one from;
http://www.auslogics.com/en/software/disk-defrag/download/
(If you try this one, try the 'Defrag and optimise (slower)' option, it can really make a difference if the pc has not been optimized lately.
The defrag options are in the 'down arrow' next to the 'Defrag' box, or in the 'Action' drop down menu.)
If you have a wireless keyboard & mouse, it's worth checking or changing the batteries.
I use 1 rechargable AA cell in my HP mouse, it lasts about 1 1/2 weeks, but I have 2 cells to use in rotation, and I have the 'other' one charged up, ready for the moment when my mouse pointer freezes.
Another program to use often, if you don't have it already is 'CCleaner', and if you do try it, use the settings as it installs, there are several options in the menus 'unticked', best leave them like that, as it's fine set up 'as is'. The 'free' version is the one I use.
http://www.piriform.com/ccleaner/download