The white screen that is coming over the top is the active desktop. The trojan will have set an image to the active desktop and when you removed the trojan the image went as well leaving a white screen. You need to turn off the active desktop. To do this goto the control panel from the start menu and select DISPLAY. Select the tab that says DESKTOP the choose CUSTOMIZE DESKTOP. In the new menu that pops up selct the tab that says WEB. In the white box in the middle of the screen will be a list of webpages that can be displayed on your desktop. Remove any ticks in the boxes next to them and if possible highlight them and click REMOVE. Click OK on this menu and OK on the display properties menu. Reboot your machine. If your desktop still comes up as white or if the DESKTOP option has been removed from your display properties menu then you have not removed all traces of the trojan and some parts of it are still active on your computer. I had this once and it was a right pain to get rid of. If this is the case then take a look at this guide on how to remove the trojan, there might be a step that you missed >>> http://www.bleepingcomputer.com/forums/topic17258.html
Hope this helps.
Steven Graham
April 2006