If you want to completely reset your laptop to it's factory state do this:
Most computers have a factory restore partition hidden on the HDD.
To get to this, when you switch on your computer and while it is booting press the F8 key or F11(HPs) until you are offered a menu called 'Advanced Boot Options'
If this does not work and windows loads normally switch off and try again.
(Some computers have a restore wizard here if so follow on screen instructions)
or
Repair Your Computer should be highlighted, if not use up/down arrow keys to highlight.
Press ENTER
Wait until Keyboard option is offered, use mouse to select keyboard, left click NEXT.
Select User Name your usual log on left click OK.
You will be offered a selection of recovery tools. One of these should be Factory Restore.
Some manufactures offer there own recovery option eg. Acer is listed as 'RECOVERY MANAGEMENT', select this option and Factory restore will be found here.
Follow option offered.
This will return your computer to how you took it out of the box.
Remember to save any important data you have on your C: drive before doing factory restore.
NOTE: THIS WILL ERASE ALL DATA THAT ISN'T PREINSTALLED. AFTER THE RECOVERY, YOU MUST INSTALL THE INTERNET SOFTWARE, VIRUS SOFTWARE, ALL UPDATES (THERE'LL BE A LOT!!), AND PERSONAL SOFTWARE AND HARDWARE. BACK UP ALL DATA BEFORE YOU BEGIN. ONCE THE RECOVERY PROCESS STARTS, IT CANNOT BE STOPPED, OR THE SYSTEM WILL GET CORRUPTED