Unusual PC performance
I've noticed recently that my PC has been performing very badly but I can't understand what I might have done to trigger it. I first noticed it using Photoshop. Even on small canvases (400x400 pixels) which used to perform normally, I now get a very "laggy" effect when I move the canvas, zoom in, drag layers around etc. I get an effect where I can see the information loading on screen, left to right and about 150 pixels high each row.
I've also recently purchased Assassins Creed 2. My PC can run Doom 3 on maxed out specs so I do not see any reason why I should not be able to run AC2, admittedly with the graphics turned down. However even at absolute minimum (800x600, everything off/low) I still get a terrible frame rate and very jerky gameplay. All this is irrelevant as today I loaded it up and voila, it was suddenly running perfectly. I even turned the graphics up and I still got a decent frame rate. I had done nothing to trigger this and changed nothing.
However, I've since turned off my PC and now I'm back to the same problem, the gameplay has a very poor frame rate. I've updated all my graphics and motherboard drivers but to no avail.
Hopefully someone has come across something similar before.
P.S. Sorry if this should be in the hardware topic, I wasn't fully sure as all my problems are sort of software related.