I don't know exactly all the libraries responsible for graphics rendering and acceleration in a common Linux PC of today but I wonder if I can install an up-to-date Linux (like XUbuntu 11.10 or Arch) on an old laptop with nVidia GeForce 4 Go 420 and have everything working (basic video playing, window composition, glxgears, I don't mean to play heavy 3D games or HD video) just fine or will I have problems (and what could be the ways of solving them)?
It looks like nvidia's proprietary driver (version 96.43.xx.xx) supports the GeForce4 Go 420: http://www.nvidia.com/object/IO_32667.html
I think in Ubuntu, the package is called nvidia-graphics-drivers-96: https://launchpad.net/ubuntu/+source/nvidia-graphics-drivers-96
With those drivers, you shouldn't have any problems with GL or using acceleration in X. Just make sure you're running X with the nvidia proprietary drivers.