How to repair monitor’s resolution issue?

Hello everybody,
I am here to get a clue for the solution of the issue, which I am facing with my monitor. The issue can be described as that the resolution of my monitor is getting changed automatically. Therefore, whenever I set my favorite resolution and better one, it automatically varies after shutting down or restarting windows. I have got installed Windows Vista on my computer and am not been successful to handle this issue.
I have tried each of my tricks for whom I have knowledge but none of them appears as asset for me to solve this problem.
To fix this issue above all, I un-installed my VGA driver and then installed it again (hoping that this should fix issue) but it didn’t worked for me to overcome the problem. Then, I tried checking my monitor for hardware faults but according to inspection there is not a minor hardware fault either.
The ending step of mine for the fixation of this issue is, I have installed a new/fresh copy of my window too but even after this I am not been able to know the solution or to solve this. This now appears to me as an issue, which cannot be done by me without anyone’s help and now I have required some suggestions.
I am desperate now to learn the fixation method of this weird issue from anyone.
Meanwhile, I want/need to know How to repair monitor’s resolution issue?
If anybody has clue about my asked question then it would be highly appreciated upon given.
Thanks in advance.
