After checking the stuff Grumpy posted, you may want to do a hardware scan of the drive. Many times in my experience missing file errors are caused by hard drive issues with bad sectors, etc...
You can scan the drive either in BIOS from a utility menu item in there if one is offered or by creating a CD from here http://ultimatebootcd.com/.
That CD has toold to scan pretty much any time of disk.
If you do see any errors, I would advise you get a new drive for the system, even if you can get the laptop working, a drive that starts to develop errors has a much higher chance of a future failure.