The installer had not made the "nvidia-installer-disable-nouveau.conf" file ... so I did it manually.
For anybody else wanting to install the latest nvidia drivers here's the full process I used:
1) download from NVIDIA web site the file <NVIDIA-Linux-(latest for your card).run> and store it on an accessible partition,
2) reboot and login as root on terminal (TTY1),
3) install the following:
#tazpkg get-install slitaz-toolchain
#tazpkg get-install ncurses-dev
#tazpkg get-install perl
#tazpkg get-install linux-module-headers
#tazpkg get-install xorg-server
4)run nvidia script:
#cp /whereitis/<NVIDIA-Linux-xf86-295.20.run> /home/tux
#chmod +x /home/tux/NVIDIA-Linux-xf86-295.20.run
#/home/tux/./NVIDIA-Linux-xf86-295.20.run
=> answer the questions (quite straight forward)
6) load the module:
#modprobe -v nvidia
7) start x session:
# /etc/init.d/slim start
8) if on a USB stick like me save a new rootfs.gz file and reboot.
Then if after you reboot you can't start slim login:
reboot using "nomodeset" as a boot option and do as sixofeight suggests above ... then if on USB stick make a new rootfs.gz and reboot ... :)
Thanks to all who helped! ... :)