Well, if it boots to the point where it allows you to start in safe mode, do that, it will only start processes that are needed to boot up the system. If you aren't getting that screen, you might have to reset the computer, or re install/repair the OS, so if you have a Win7 disc, or whatever OS you have, put that in your laptop and select repair, if you want to reset, select re install or install.
There aren't many other ways you can get into the system, if the OS is messed up, you might have to wipe the harddrive and get a new OS.
At this point command prompt isn't going to help much.
Hope this helps!
~Sevenater