Trojan attack on my system(Plzzzz Help)

Recently my system contacted some virus and am finding it difficult now to do things in my system.
this is what is happening to me now…

1.The virus disabled my cmd
2.My notepad isn’t opening
3.It also locked my desktop i.e. after booting, my desktop icons disappears.
3.Cant install any anti virus.
4.No application is opening

now the worst of all is all that i have very important documents in my system.
i also downloaded A Personal Security virus cleaner, after scanning, it reveals all the attackers including, Trojans, malware, sypware etc
but when i want to remove/clear it from the system, am been asked to insert the activation code. plz could any one in here help me out with this

Please do the steps mentioned on the first post (Essexboy) here:

http://forum.avast.com/index.php?topic=53253.msg451454#msg451454

Personal Security is rogue antivirus and is virus by itself

removal guide: http://www.bleepingcomputer.com/virus-removal/remove-personal-security

i also downloaded A Personal Security virus cleaner, after scanning, it reveals all the attackers including, Trojans, malware, sypware etc

Personal Security is rogue antivirus and is virus by itself

removal guide: http://www.bleepingcomputer.com/virus-removal/remove-personal-security

YEah i opened the site above and it is exactly what is happening to my system.
it keeps given me some alert after scanning about some infections. some am trying to download the Malwarebytes Anti-Malware, but i want to know if there is any activation code associated with it?

Malwarebytes Anti-Malware, but i want to know if there is any activation code associated with it?
No it is free and follow the removal guide step by step

There is no activation code for MBAM, download the free/trial version which after 30 days reverts to the free version.

Thanks am so gr8ful, will do that at once

No problem.

Welcome to the forums.