How to know if your computer are infected by virus or any related programs?

Here is the article on how to determine if you are infected by virus or any related files or programs.

1. Your computer slows down. In many cases, your computer might get slows down due to virus infection. As you are getting infected with those files, you will loose some of your important data's, files and programs and may lead to system crash. Sometimes, the memory of your computer will be decreasing due to worms or other infecting files duplication within your system. It's better to stop it and recover as early as possible time.
2. Too many pop-ups appear without your consent. Sometimes, there will be pop-ups specially when you are browsing the web. But if you got those pop-ups strangely, you must suspect that your computer is not in normal situation.
3. Try to access this following programs.

• Task Manager by pressing Ctrl + Alt + Delete on your keyboard.   

 If you will receive this following message. "Task Manager has been disabled by your administrator", then maybe you got infected. 

• Run command by pressing Win Key + R or Go to Start>Run

Accessing your Run command can be more reliable than locating every application in the list of your Programs. Run command has the ability to access files such as registry editor command prompt and other related windows programs in your system easily. If you got this message when trying to access your run command:

Your possibly get infected.

• Registry Editor through Run and type regedit.exe

Your Registry Editor or Regedit.exe is one of your system files that has a big role upon storing values and informations of programs that has been installed in your computer. 
If you got this message, probably you are infected!

• Open any folder or "My Computer" and navigate to Tools and look for Folder Options

Refer to the image below:

Once you got infected, most of virus or any related infecting files hide the "Folder Options" menu. The reason why virus hide the folder option in your computer is to protect itself to be naked to your eyes. One of folder options ability is to "show hidden files and folders" in your computer. 
Note: Virus and other related programs set it's attributes to "hidden"

• Command Prompt - open Run command and type cmd

 Got this message? If you do, then you computer are merely infected. 
Now, if you found one or more inaccessible programs I listed above, then you must have to restore it back again by first reading the article "how to delete virus manually without using any anti-virus programs". Then restore the access of each of those system files, by reading this.
"Restore the access of your important system files that was altered by virus or any infecting files."