i havent tried reformatting windows yet. but why would it safe normally when its windowed then. doesnt make sense to me. it has so many bugs. i know its a great game. but its too buggy. just too buggy.
I havent had any bugs other than the week10 crash the patch fixed. If there were any major saving bugs we would ALL be getting them, and it would not be limited to a handfull of cases. Therefor you have something in your system affecting the stability and performance of PES, for which the game can not be blamed.
Windowed mode and fullscreen have different priorities for different applications, and example would be in Vista. Vista will auto disable the Aero effect in fullscreen 3d applications, but if they are run in windowed mode Aero remains active.
Theres no need to reformat windows unless you have let it get in a terrible state performance/stability wise. A clean boot can be done by simply using the MSConfig tool.