If it's only a few months old, then you should still have warranty on it. You could check it out. However, if there is important data on the laptop, you might try to secure that, before sending it in.
Something you could try:
Boot in safe mode (repeatedly press F8 as your laptop is booting up, until you get an options menu, which allows you to boot in safe mode).
If you can log in while in safe mode, go to control panel, users, and add a new user.
Reboot the laptop, and see if you can log in as the new user.
If that doesn't work, I wouldn't recommend you to try much on your own. Since it's a laptop and you can carry it around, do you have the option to bring it to a knowledged friend?
Finally, do you have a Windows install DVD with your laptop? If not, the installation program is most likely on a hidden section of your harddrive. You most likely have some option to restore everything to factory settings (check the laptops quick reference sheet if it has one, the manual otherwise), but that would wipe out all the data you put on it.