Open a terminal window (xterm or something) and try the following:
1. Type su and press the return/enter key
2. Type your root password (Default for the LiveCD is root)
3. Make sure your connected to the internet for the next step ;)
4. Type tazx and select to install or reconfigure xorg and allow it to download the lists it need.
5. Select the closest driver to what you have and then allow it to install everything then exit tazx.
6. Type tazhw --detect-pci and allow it to scan your devices.
7. Type tazpkg get-install xorg-xrandr and allow it to install.
8. Type wget http://trixarian.za.net/downloads/lxrandr.tazpkg and allow the package to download.
9. Type tazpkg install lxrandr.tazpkg and allow it to install.
10. Now go to "Red Spider Button" --> Preferences --> Monitor Settings and pick the resolution you want.