Blank screen after update

[Jonathan Precise]

You probably have a root account, and setup a password for it. THIS IS NOT RECOMMENDED!!!!!!. Enter your password, and press enter. Post back any errors.

[johnwill]

Hello.
After many attempts I am no nearer regaining Ubuntu and am now very frustrated, I am back on Windows 7 having had to suffer a Trojan horse attack,and to attempt to download Kb3 for windows and ending up with several unwanted programs.
Where do I go from here?have I lost Linux.
When I attempt to Log on Ubuntu still shows as an OS, so I assume I still have a dual boot system: i have attempted to Log in recovery mode as the wizards on these forums have been kind enough to guide me through,and try to follow their instructions,obviously without success,it must be something I am doing wrong,!!!Oscar Wilde said: It is far more difficult to talk about a thing than to do it.
Doing seems to be my problem.
Please Help.
John