When I start up my computer the power up self test screen fills up with what appears to be random dots & unrecognisable characters allthough the graphic displays correctly & is in colour. I can tell that the underlying display is the p.o.s.t screens by the way that the screen fills up & I can tell that the memory test function is trying to display by the position on the screen and the way that the charcters rapidly change as it goes through the test even though I can't read the characters. After the p.o.s.t. screens the windows welcome screen appears as normal & is displayed correctly. The screen blanks then changes to the blue screen with the following error message :- Stop: c000021a Fatal system error. The windows logon system process terminated unexpectedly with a staus of 0xc000012f {0x00000000-0x00000000} the system has been shut down. The characters on the error screen are also displayed correctly. If I insert my Acronis true image cd into the cd drive & restart the PC, the Acronis application starts ok & displays ok. I have searched on the net for info on the error message to no avail, but I suspect that any solution would be difficult to implement as I can't boot into windows & can't read any of the screens in the bios setup either.
Could any one suggest a possible solution to my problem as I don't know if it is a software or hardware problem & if it is a harware problem which piece of harware do I replace.

Many thanks Dave

Hi Dave and Welcome to D-A-L.

Unfortunately, you told us nothing about your computer.

Laptop or PC?

Store bought? Make and model?

Home/custom built PC? Motherboard make and model?

On board graphics?

Graphics card? Make and Model?

Version of Windows?

When did the problem start? Did you recently add or change hardware?

First guess would be a problem with the graphics system and I would try another monitor. If the problem happens with that monitor, then you know your original monitor works. That points to your graphics card, or motherboard if using on-board graphics.