After installing "Best Malware Protection" I found fake errors in system, I tried to close this with task manage but task manager was not working. I tried to uninstall but no any install file. So I googled and found solution.

Solution:

(1) Right click on the short cut of "Best Malware Protection". It will show you a path 

     "C:\Documents and Settings\All Users\Application Data\b35a5d\BMb35_2129.exe" /hkd

      C:\Documents and Settings\All Users\Application Data\b35a5d - b35a5d may be random number.

(2) Click run - Window + r and place this string (C:\Documents and Settings\All Users\Application Data\b35a5d) in that and open the root folder of "Best Malware Protection" There are many files, Delete one by one.... All will not delete. If not able to delete then Go to "Run" and type "MSCONFIG". Check there entry of "Bmb35_2129". Un check this so that it may not run in next startup of PC. Now restart the PC.

(3) Now you may be able to delete all files related to malware.

(4) Now go to "windows" directory. Locate the "taskmgr.exe" click on this. It will not open the task manager. :) Now rename this file like taskmgr1.exe now double click on this. It will open the task manager. It means there is no problem with system file. Problem is with the registry key.

(5) Now time to correct the Task manager. open the Registry

run > regedit

(6) Go to following path

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options\

(7) Delete Key File: taskmgr.exe.

(8) If not found the entry, Go to edit > find and paste there taskmgr.exe

(9) After found the entry, now check the path. It will be "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options\"

(10) now delete the "taskmgr.exe"

So whats up.... your PC is looking fine :D... open tha task manager as you want to open. from task bar, from run, from system32 folder.