Hi.There has been problems with Flash player on Vista that has been causing computers to crash.Normally when they try to update to the latest version of flash they get problems that so far have not been resolved.
probably not your problem but thought that I would mention it as you are not getting many replies.
Maybe download and run Malwarebytes free edition update it first.That should find anything that your security programs may have missed.
Maybe try a disk check.
Right click C Drive.properties. Tools.Check now.And tick both squares.It will start automatically the next time you reboot your computer.It will take about an hour or so to complete.Any problems it finds it should repair.