My toshiba satellite l455d-s5976 laptop is only giving me a blank/black screen after the welcome screen. what do i do?

I assume you are running some version of Windows.

This may be a Thinkpoint infection. When you reboot the computer, hit the F8 key several times before Windows starts up (once should be enough, but you have to do it at just the right time). When the Safe Boot options list comes up, choose "Safe Boot with Networking". If you get a "Thinkpoint Security" splash screen, this is your problem. Thinkpoint is a fake anti-virus program. It is itself the virus. It will want to "scan your drive". It will not let you do anything else. When you tell it to scan your drive it will pretend to do so and will "find" numerous problems. Then it will demand you pay a ransom of $60 - $80 to "fix" the problem (probably to a Russian criminal organization), and will disable your desktop. If you try to restart, Windows will tell you that "hotfix.exe" is blocking the restart process. Newer version of Thinkpoint/hotfix also interfere with the Task Manager so you cannot use it to force termination of hotfix.

Here is the repair: First, download a copy of rkill.exe and Malware Bytes Anti-Malware and save them to a USB flash drive. On the Toshiba, plug in the flash drive with these two files, then press the Windows key and the R key simultaneously. This will bring up the "Run..." box. Type "explore.exe" (no quotes). This will bring up your Desktop, and let you get into the flash drive. Double-click rkill. This program will stop Thinkpoint (runs under the name "hotfix.exe"). Now double-click mbam (the Anti-Malware program). Tell it to do a full scan on C:. You should see hotfix on the list of rogue programs found. When the scan is complete, let mbam fix all problems. Next, update your anti-virus program and check the scan schedule to make sure it is set for a weekly time when you can leave the computer on for this activity.

How does Thinkpoint get in? If you get a pop-up window warning you have a virus infection, DO NOT click it - that is its entry point. Immediately quit all web browsers and start a scan (e. g., with mbam) for spyware and adware infections (tell the program to update its definitions files before starting the scan). This will safely get rid of the pop-up. Run Windows Update to make sure you have all of the latest security patches.

Can you please be more specific?
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Is it after the Toshiba logo or Windows logo?