I have a laptop and a desktop at home , both with pretty good processors and GPUs , which can easily run a game like Crysis 2 or Black Ops at 30-35fps at max graphics.

That was the report i took a year ago , however these days , i noticed a few strange issues.

Firstly , when I formatted my laptop's hard disk a month ago and reinstalled my old OS and ATI drivers , i noticed that Assassins Creed which ran at a good 45 fps before the format , came down to around 20. I cannot find why this is happening seeing that the drivers are same.

Secondly , my desktop , which ran Assassins Creed at 50 fps started to behave rather strangely. When i woke up in the morning and started it up , Assassins Creed ran at just 30 fps. I was puzzled . I got confused and just went off for a morning walk. When I came back , and started the game again, it ran at 45fps. That makes sense because I always play games only after I let the desktop run for a few hours as i have a habit of turning it on and then going off to do any work that I have. And by the time I come back , it runs pretty fast.

So , my question here is , WHY is this happening?
Does anyone know any issues of graphics card getting worse as they get old? Or graphics card not working upto thei max until the computer runs for a while? Or graphics card disfunctioning after a OS format?

Any ideas or suggestions would be helpful