Hello grive and welcome to Seven Forums.
Have you tried booting into Advanced Boot Options? As soon as you start your machine click the F8 key (top row of keyboard) and keep clicking until you see the Advanced Boot Options screen. This tutorial has a bit more info. Advanced Boot Options
From here you should be able to choose from several different options including Safe Mode, Last Known Good Configuration, etc.
Depending on your specific computer you may also have a hidden recovery partition that can return your machine to factory specs (just like the day it was when you got it home.) On some laptops you can press F9 at start up and that should open the recovery process. I believe you get four different options:
1. If none of the following recovery options is selected, the computer will just be rebooted to load Windows (if Recovery is started from the hard drive) or run the bootable disc in the optical drive.
2. The first partition is deleted (the others remain intact) and a new system partition C: will be created.
3. This option removes all the partitions from the hard drive and creates a new system partition C:.
4.This option removes all the partitions from the hard drive and creates two new partitions C: (60% of the drive’s storage capacity) and D: (40%).
You might want to check your owners manual or quick start guide to see if it gives more info.