How can i get onto my desk top?

An automatic update failed, maybe because the computer was improperly shut down, and the computer was left in an unstable state.

Restart in safe mode.
Try restoring to a previous restore point.
Clear the internet cache.

If that DON'T work, do the following:
In safe mode. Open the registry editor: from the Run dialog, type "regedit" and press the enter key.

Find the "RunOnce" keys (there are 2 of them), they are:
HKEY_CURRENT_USER\software\Microsoft\Windows\CurrentVersion\RunOnce\
and
HKEY_LOCAL_MACHINE\software\Microsoft\Windows\CurrentVersion\RunOnce\

Delete everything they contain except the default entry.
The (by default) entry must have (undefined value) in the value column.

This one of the safe registry editings. Those keys are used to start boot time maintenance tasks, like replacing locked files after an update or installation, and are normaly erased after those tasks are completed.

Reboot normaly and clear your internet cache. Let the auto-update redownload the failled update and apply it. Be sure that the update is completed before you shut down. It may be a good idea to not do anything while the update is working. Reboot once you get the message telling you that the update is done.

Electro
January 2012