Please do try these troubleshooting steps that may help in solving that issue.
- Do a hard reset first, remove the battery and AC adapter then press and hold the power button for 20 seconds then try booting up again.
- Next is to try and load it in Safe Mode, while the laptop is booting up repeatedly press on F8 until it loads Advanced Boot Options, select Safe Mode and press Enter.
- Once in Safe Mode try logging in and see if it would load normally. If it does load try performing System Restore, restore it back to an earlier date or time before the problem even happened.
- If all these will not work the last resort would be to perform a complete factory reset.