I would first go to where you bought that computer and ask them for the disk they owe you. Then I would try an install without a format to replace all the missing files. That may not go well. You have a lot of damage, but you can try it.
Otherwise, you will need to format the drive and reinstall from scratch. Either way, you absolutely have to have an Install CD.
Start saving your files and program installs, any drivers you downloaded etc. Do you have a Burner? Or possibly other partitions to save to?
To run scandisk, you have to do a CTRL+ALT+DEL and shut everything down but Explorer and systray. Then go and change your screensaver to none.
Type Scandiskw into the Start>Run box and press enter.
When the program starts, Choose Standard or thorough (but you found your cause. Sircam. )
Click the advanced button and be sure to select Free Lost file Fragments or you could have a ton of useless files on your C Drive.
Scandisk takes no time at all if you are only checking your files. If you suspect disk damage, a thorough Scandisk takes a while. While you run scandisk, leave the computer. If you so much as movbe the mouse, it will have to start over again. Let it run until it's finished.