Hi Dene,
You should consider upgrading your video card to at least a 128MB Geforce 6200 (AGP). They cost around $45 USD or ($95 NZD). It is a DirectX 9c part, and is OpenGL 2.0 compatible, and uses Pixel Shader Model 3.0. This is currently the bare minimum most modern 3D games (ie, Doom3, Battlefield 2, FEAR) will require, and is more than enough for flightgear. An as a tip try and avoid buying anything older than geforce 6x00. As the technology on cards prior to the 6 series is quite outdated.
In the mean time, if you want to use the low res textures, you will have to rename the textures.hires directory to something else. I think Pigeon has the fgroot directory installed somewhere in the /opts directory. However, you can always find where the flightgear textures directory is located by running the update database command from a terminal:
updatedb
and then the locate command to find what a file or directory you are looking for:
locate textures
this will generate a listing of the where the textures are located. When you want to rename a folder (from the command line) type mv /the_directory_name to_the_new_directory_name
