800x600 Change

Wonder if any one can give me help me please.
Am trying to change resolution of my screen t 800x600 with 16 bit.
it looks whenever I select the screen size from adapter section of settings.
it change the monitor but the bit is 4 and not 16 bit.
If I select the 16 bit from the setting section.
somehow monitor goes back to it's original setting. I followed the instruction bellow.
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Click the Start button, point to Settings, and then click Task bar
& Start Menu.
The Task bar & Start Menu window appears.
On the Task bar Options tab, click to check the box next to Show
small icons in Start Menu.
Click Apply.
The entire Start Menu should display without having to scroll.
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 When I go to task bar section there is no area to tick to show the small icons in start menu{  i HAVE  WINDOW  XP }. and when I follow the on line support link. there is exactly what I have already followed my self

.  {wonder if any of you can shine some light please?}
 be happy to hear from you.

Many thanks in advance.

FROM MOEEZ

   Bye

P. S

I have problem with this as I'm trying to install Britannia encyclopaedia and installation cancels it self even after trying to lower resolution all the time. I welcome your help which I can use for future updates too.    ;)