Any program is not running on my xp, what should I do?

I have been using my current operating system for the last one year. I didn’t get any major problem in it. But last night I got a weird problem that any of the programs of my PC was not running. I have a habit of keeping the shortcut icon of all programs on my desktop. All icons were present on the desktop, but nothing was happening when I double clicked on them.
It’s a really weird problem. I don’t know what I should do now as I don’t have much knowledge on computer trouble shooting. In spite of lacking in computer knowledge, I tried to restore my PC to an earlier date, but I got no result.
Can anybody help?
Any help will greatly appreciate.
Thank you.
