Why isn't my computer working?

I have a windows vista. It is only a few months old, but all of a sudden it stopped working properly. The clock and calender that usually appears at the side of the screen doesn’t work and any kind of javascript pop up windows don’t work anymore. This includes videos and downloads.
One site i went on said that I had javascript turned off but i checked and it is on. Another site told me to download the newest flash player, but the pop up window for the download didn’t come up. It was working perfectly two days ago but now it is messed up. what’s wrong?