Change default screen orientation when spinning the screen.

Not sure if that model supports screen rotation; but if it does it won't be in Control Panel ==> it will be in the screen properties settings.

Right-click anywhere on the desktop; select Properties; click on the Settings tab; then click on Advanced and see if there's a "rotation" setting.   If so, that will let you do what you want.

... Note that this setting is at different places within the Display Settings area with different graphics drivers ==> so look around a bit and see if you have the ability to modify the orientation.

Yes, my screen supports rotation, even it has a button for it.
I can change rotation in the control panel too.
My problem is another one:

When I spin the screen to convert the laptop into a tablet pc (no keyboard), it automatically rotates from landscape to portrait. Then I have to rotate screen manually to landscape again.  I want to avoid this.

If you manually rotate it;  then shutdown, Windows should remember the settings; and the next time should be in the same orientation ==> have you tried this??

It remembers when I reboot in tablet mode. But if I spin to "laptop mode" and back to "tablet mode" it doesn't remember.

Well ... I looked through the manual and there's no indication of a method to change the default orientation.   If the BIOS doesn't have a setting for the default for each mode, then you probably can't change it.

... but it does have a very-convenient "rotate" button ==> so it seems like this is not a particularly onerous task :-)

>>If the BIOS doesn't have a setting for the default for each mode, then you probably can't change it.
no, bios doesn't have an option.

>>... but it does have a very-convenient "rotate" button ==> so it seems like this is not a particularly onerous task
not exactly. when you rotate from portrait to landscape, desktop icons change in position. also I have to press this button 3 times for the orientation I require.

According to the XP Tablet Edition help screens (I just looked), you can set the default orientation in "Tablet and Pen Settings" in Control Panel ==> AND you can set the Sequence in which the orientations will change with the "rotate" button.

I just checked in a copy of XP Tablet PC I have installed in a Virtual PC and these settings are indeed there.   I can't test it, of course, since the virtualized PC doesn't really have a tablet :-)

This MAY let you set the orientation you like;  but if not you should at least be able to change the sequence so a single press of the "rotate" button will orient the screen the way you want.

yeah, i have been there before, trying to avoid the portrait issue. I have changed the sequence to press just 1 time the rotate button. It works. But still this doesn't solve the problem of the icons rearrangement in desktop.
Anyway you have some points so far ;)

I'm surprised the icons aren't kept in the same relative positions.   Have you checked the settings for "Arrange icons by" on the right-click menu for the desktop?
Be sure "Auto Arrange" isn't checked ... that may be what forces the rearrangement.

the problem is when you are in landscape position, some icons can be on the right side, when you change to portrait, those icons are moved left-wise to keep inside the screen, when you change again to landscape, the icons don't return to its original position.

Seems like a simple enough thing to resolve => just arrange the desktop so there aren't any icons so far to the right that the re-alignment causes the issue.

your solution doesn't answer my question, I think my momma can tell me the same.
Some times I have lots of icons and best way to organize is near to borders and corners according to use.