Toshiba laptop display corruption. I switched on my laptop and suddenly, lots of coloured dots appeared on the screen until I could barely see anything. what could this be?

A line vertically down the screen (usually bright green) is a failed column strobe. This can be caused by the connections at the top of the screen failing or the strobe chip starting to die.

Random colours can be caused by a cracked screen or a failed video card.

Best to take it to a repair shop for it to be assessed.

What your describing is a major video problem, poor color and it is blurr, It would be far cheaper to replace the monitor with a new one.

Although your Toshiba portable computer appears to be on and running, there is no image on the built-in LCD display screen Look closely at the LCD display screen. If you can see a faint image on the screen, the display screen's fluorescent backlight may be turned off. Shining a flashlight directly at the screen will make it much easier to see whether or not there is a screen image actually present, though not lit up. On most Toshiba portable computers, there is a small plastic or metal pin near one of the LCD display lid hinges. When the display lid is shut (closed), this pin is pressed against an internal switch which turns off the backlight, saving battery power. You may be able to turn the backlight on again by tapping this pin repeatedly. The normal screen image will then suddenly appear, or re-appear.If there appears to be no display image at all, the problem is probably not related to the backlight. In this case, press and hold the Fn key and then press the F5 key several times, pausing several seconds between each keypress. This will cycle through several display output modes: Internal, External, Simultaneous, and possibly one or two more.If no image appears on the LCD display after cycling through the Fn-F5 sequence, try doing so with an external CRT monitor attached, if possible. If you still see no image, on either screen, try restarting the computer with the CRT monitor connected.If you see a screen image that looks normal when the computer is first powered on, or when you try to enter the BIOS Setup during the power-on sequence, it's an indication of a software problem (a driver or an application that's launched while the computer is loading Windows, possibly). Try downloading the display drivers for the computer from the Toshiba Support website, and then re-installing them.If the LCD screen or an external CRT monitor is blank only while the computer is first powered-on, but then works fine, it's probably not an indication of a problem. Some models display no text or images during the startup process. Additionally, installing some Windows Updates may delay the appearance of the familiar Windows desktop.If there are blank margins bordering the image on the LCD screen, launch the Windows Control Panel, then double-click the Display icon. Click the Settings tab, and then adjust the Screen Resolution setting until image fills the entire LCD screen, which will cause the margins to disappear.If the font size on an external CRT monitor seems too small for comfortable viewing, try clicking the Advanced button on the Settings page, and then adjust the DPI (dots per inch) value. Try 120DPI and 135DIP, to begin with. Avoid changing the DPI to much greater values, in order to avoid settings that will be difficult to change.

1. Hold down the power button for approximately 10 seconds until the computer turns off.
   
   
2. Verify that neither one of these keys are stuck in the down position:
   
   the Tab key (arrows pointing left and right)
   
   the tilde key ( ~ and ` characters)
   
   
3. Turn the computer on.
   
   
4. If either of the keys above appears to be stuck in the down position, and if the issue is not corrected by pressing these keys repeatedly, then service is required.

hardware, try to connect with external display via VGA connectors.. see if you have no issue to load the OS. If you still have problem, then your O/S might be corrupted you need to reinstall it but make sure you have the drivers on it. you can check the drivers here. if you don't have.

Could be try connecting to an external monitor using the vga port. If the same problem appears on the external display the problem is most likely the video card. You may wan to update the display drivers.

If it is a lcd screen, the screen is taking a dump on you

either you darkened it or the back light went out. try the briten it with the FN key

Try to reinstall the video driver from Safe mode.
It appears your hard disk is OK but the operating system and or registry is corrupted.
1. Try installing the video driver first.
2. If it still does not work, back up your data files in Safe Mode then re-install XP again, make sure you delete the partition and create a new partition and do a full NTFS format, not a quick format.

something fried .. sounds like the vertical has gone ,
call a tech.