My Windows 7 Home Premium Dell Desktop displays upside down on my Samsungn SyncMaster 2494LW monitor

Dell site offers Vista. You may get it run in compatibility mode.

http://www.dell.com/support/drivers/us/en/19/Product/dimension-5150x

If you are in Windows XP, you can use the following key combination:
CRTL + ALT + up arrow
I am not sure if this combination works in Windows 7.
Good luck.

make sure that you adjust its resolution to 1600 X 900

best regards

If you have an optional video card installed in your system, try plugging in the the monitor using the 15 pin VGA plug on the back of the computer and see if you get the same results. There might be a plastic cap covering the VGA plug so you'll have to remove it for testing purposes. If no change then try using a different monitor. You can also try plugging the monitor into a different computer.
If the monitor display is normal using the VGA port then your graphics card has a problem. If the monitor is still dark attached to a different computer then your monitor or monitor cable is bad.

Windows 7 has some neat little enhancements, one of them being how it lets you handle dual monitors. If you're adding a second monitor to your Windows 7 home or office PC, which is a very good idea, it's a breeze to configure.
There are actually two ways you can currently setup multiple monitors in Windows 7, either by using a keyboard shortcut or via the traditional system properties.
I really like the first method since it's new and is way easier than having to go into the Control Panel or anything else.
Simply press the Windows key and P (Windows + P) to bring up a quick menu of options.

Pretty neat! You can pick to show only the computer, make the second monitor a duplicate of the first, extend the desktop to the second monitor or turn off the first monitor and activate the second.
The second way is to right-click on the desktop and choose Screen resolution.

Now you'll see the familiar 1 and 2 to distinguish which monitor is which. There are several options and under Multiple Displays, you can choose from the same options as when you pressed Win + P.

That's it! You can also change the orientation of the displays and change the resolution of each display. It's pretty straight-forward in Windows 7 and a lot easier! Enjoy!

down load ur latested free drivers from the following link

download.cnet.com

This should be a very fast fix.
First try pushing the Shift and Home key at the same time.
If that didn't do it,
Right click on the desktop,Click graphic properties,Click display settings,Uncheck the box "Enable rotation" and click ok.

Hi,
Try holding down the CTRL key + ALT key and tap on the Up arrow key once to rotate the display back to orginal orientation


Thanks
proton

http://forums.techguy.org/tech-tips-tricks/336002-windows-xp-flipping-screen-upside.html

Windows XP: Flipping the screen upside down and back again


Once, at University, someone had flipped the screens of all the public computers (running on Windows XP) of the English Department upside down. The wallpaper, desktop icons, fonts, mouse-cursor and even the start-up screen...everything was displayed or moved upside down. People could not check out their e-mails or surf or do anything.
To reverse the upside down screen mode, press ctrl, alt and the up arrow (arrows console) at the same time; the screen will probably go blank. Turn off the monitor, turn it on again and the display will be normal again. If you possess a sense of humour or are antisocial, press ctrl, alt and the down arrow simultaneously, turn off the monitor, turn it on again and everyone (excluding the culprit) will be desperate --> upside down! Works for Windows XP Home and Prof.

press alt + ctrl + the up arrow