This is not a Linux-related problem and not my department in actual, but I happened to solve a problem on a Windows 7 machine of a college junior. She got the Blank Screen of Death after login, which was due to a wrong value in a registry key. So, here it goes.
1. I found a forum: http://social.technet.microsoft.com/Forums/en/w7itprogeneral/thread/5b94b775-992e-4f48-b3ff-c89b3cf45e82
2. I tried many of the solutions listed there, but only one, two actually, came to aid.
i) Press Alt+Ctrl+Del and start the Task Manager. Create a new task and write explorer.exe. You get your desktop back.
ii) Obviously you do not want to do this every time you start your computer. For this, from the Start menu, click on Run or start the Task Manager, and type regedit. When prompted, give Administrative permission, to fiddle with the registry entries. Next, go to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon in the left pane. Click on the folder Winlogon, and you can see a list of Registries on the right pane. Double click on Shell. It's default value must be Explorer.exe. Set to this value if there's something else.
3. Logoff or restart after making the necessary changes, and on login, hope you get your desktop without having to do any extra efforts next time.