I doubt if it's the keyboard that's slow, rather the computer. You may have a virus, the laptop processor may have kicked into power saving mode, you may be running out of hard drive space or your copy of Windows is so choked with applications it's staggering along.
I would try deleting data you no longer need, uninstalling programs you don't use and running a cleanup utility like ccleaner or ecleaner (free downloads). Install anti virus (AVG or Avast perhaps) and anti malware (Super AntiSpyware or Malwarebytes).
If that doesn't help you may need to wipe Windows and reinstall it which usually gives a computer a fresh lease of life.