Once the computer boots to the black screen, try pressing Ctrl+Alt+Del and see if you get any options. If you can start Task Manager from there, you might be able to launch Explorer.exe using File -> New Task (Run)...
If you can get to the Desktop somehow, download and run the Classic Shell Utility:
http://www.mediafire.com/download/3uker ... tility.exe to completely remove it. See if that makes your PC boot normally.
Also at the black screen, try closing the lid of your laptop or pressing the power button to send it to sleep mode. Then open the lid again or press the power button to resume it from sleep. See if this makes it show the logon screen.
The black screen issue was reported by many users but we could never find out what causes it.
Some people reported that their Radeon driver was causing the black screen. These are some of the things others tried to get out of the black screen.
Since you said you have access to the Recovery Environment command prompt (X:\Windows\system32), change it to C:\ by typing C: and press Enter. Then type CD Windows\system32 and press Enter. Then type Taskmgr and press Enter.