Toshiba Windows Vista resolution problem

Depending on the version of A100 you have, 1280X800 may be the max resolution for your graphics card. Read the user manual for your specific model to see what the max resolution is, but usually, the video driver will lock out resolutions that your screen cannot handle.
If, for some odd reason, your screen can handle a higher resolution, try updating the video drivers.

Now to answer your other questions;

• There is no 64 bit color mode; and if there was it would be redundant, as humans can't see that many colors.
• 60Hz is fine and is probably the best your monitor can do.