This symptom (blank screen with cursor at the top left side of the screen) in most of the cases indicates Hard Drive issues. I can try assisting you with troubleshooting. Please try the below mentioned steps and check if this helps:
1. Power off the computer and disconnect all the power sources and external devices.
2. Press and hold the power button for 10-15 seconds and then release.
3. Put the AC adapter and battery back and power on the computer and check if the computer boots normally.
4. If the computer doesn't boot normally in step 3, check in the BIOS if the Hard Drive is detected.
5. If the Hard Drive is not listed in BIOS, Load the BIOS Defaults and then restart the computer.
6. If you again get the same screen, take a technician's help to reseat the Hard Drive (if you wish to do it yourself you can refer to service manual).
Note: Before you start working with insides of the computer, please go through the pre-removal instructions mentioned in Service Manual, this is for your and machine's safety.
7. After reseating if the Hard Drive is not detected again, you need to replace the Hard Drive.
8. If the Hard Drive is listed in Step 4, run the Diagnostics provided by the manufacturer on the Hard Drive.
9. If the Hard Drive Test gives any error please contact Toshiba support for further course of action.
Some of the steps mentioned above are specific to system models, if you need steps on how to them, please reply with the exact System Model Number of your Toshiba Laptop.
Do reply with results.
Thanks & Regards