Tentative repair of a Sony Vaio notebook with damaged nVidia graphics card.
This particular notebook has two modes, Stamina and Speed, which basicly switches between the onboard intel 945 chipset graphics in Stamina mode and the external nVidia card for Speed mode. The Speed mode has its own dedicated memory for graphics.
I noticed that the graphics garbled screen was only present in Speed mode, hence the defect is present only for Speed mode.
This is usually due to a defective soldering of the BGA chips, which can be solved mostly by applying no-clean flux and localized heat.