Give it a Birthday you’ll be surprised, it will be as new.
From a completely mains off situation
Switch on and immediately and continuously tap F8. (This F number can be manufacture dependant) You must start from a power off situation. Until this action brings up on screen a selection of options. This is most important; you must achieve this before proceeding. Try F10 for example
One of which will be: - Select “Repair your Computer”, enter. Follow the on screen instruction but for the best result, select the top option “Full Destructive Recovery” if/when presented, don’t be timid, go for it.
Follow the on screen instructions Click start, enter. All you can do now is to sit back and relax, go for a coffee, leave it well alone let it do its own thing, it’ll take about 30 minutes.
Don’t bother to install any drivers (e.g. printer) asked for during the run up as this can easily be done after you have your pc back, in your control. Then spend time to get all, or most, updates in before you start loading your own software/games
PS if you need and have trouble getting “Windows Vista Service Pack 1 (KB936330) Google it