Do you have a recovery disk?
It may of come with the laptop on a cd or dvd.
If you do not.
Most laptops have what we call a recovery console.
It will depend on your laptop, it`s brand name and model number.
Mostly it involves powering the laptop up, holing the power button down.
Or before it starts windows pressing an F1 to F12 key on the laptop.
Most laptops contain a hidden image or partition where the initial Os was installed on the laptop and can be accessed by this option to reinstall the windows or repair it, if the windows recovery fails.
If you have the manual please consult it on the process.
Or search online for the PDF version of the manual for the brand name and model number of the laptop.
If you can not do this then name the brand of the laptop.
And its model number, that can be found on the under side of the laptop on a sticker.
Then we can point you in the right direction to fix the problem ok.
Hope you see this and it helps. For Win8, press F9 as you are starting the computer. It isn't safe mode anymore but it gives you 3 options. Refresh will uninstall all your software, but at least it leaves a file on your desktop with clickable links to help you re-install most of them. The second option does a factory reset. Didn't check the advanced options because Refresh and re-install did it for me (Asus ultrabook running Win8).