Dell XPS L502x Laptop (windows 7) won't start-up

I changed the start-up options and disabled start-up for what I thought were non-essential programs that were slowing my computer down. After trying to reboot, it says it is unable and asks to start startup repair. I have tried most of the options including system restore and even the dell data-safe factory update restore and it still will not take me to the desktop. It endlessly tries to do the start-up repair and restarts or shuts down. Any advice would be appreciated!