Account closed as requested
you surely have GeForce graphics card(s); nForce is nVidia chipset present on some older motherboards. If you don't know which mobo you have, CPU-Z program may help - it detects some mobos. Also check your processor type.
- download Display Driver Uninstaller and wushowhide.diagcab (you may use google to find them)
- run DDU as admin (safe mode is not needed), uncheck Reboot box, click to Uninstall, don't reboot
- immediately after that run wushowhide, untick Fix automatically, Next, click to Hide updates
- select all that nVidia stuff, click to Hide button
- restart; your system shouldn't install new nVidia drivers anymore
- download 314.22-desktop-win8-win7-winvista-64bit-english-whql.exe from nVidia site if you have 64bit system or 314.22-desktop-win8-win7-winvista-32bit-english-whql.exe
- run as admin, Custom Install, select only vga driver + hdmi + physx, nothing more.
Please remove your 550Ti card first, then downgrade driver - it may help. If it doesn't, then use HWMonitor program - it shows temperatures and fan speeds of both processor and graphics card. Observe them while opening your big data file (in which program?) As the next step, I recommend to borrow and try some Radeon card.