Try pressing Ctrl Alt F1 from normal mode or try booting into fail safe mode and once you get the terminal, login and backup ur xorg.conf and edit it to change the driver to vesa. Save and exit and reboot.
Once you get into normal mode -
cp /etc/X11/xorg.conf /etc/X11/xorg.conf.bak
(Under "Device" Section, change value corresponding to "Driver" to "vesa" (instead of nv or nvidia or ati or intel). You need to press INSERT key to write values and then press ESC key to stop writing.Type :x to save and exit)
shutdown -r now
1. If you have ATI or Nvidia card, install the respective drivers first.
2. If you are using openSUSE 10.3, you can install Compiz Fusion with 1-click install available from the website: http://en.opensuse.org/Compiz_Fusion
3. Then Enable Desktop Effects or open Compiz Fusion Settings from the Application Browser.