How to connect 2 PCs at the same monitor or display

There are at least two methods:

The first method of course is to use a graphic display that has 2 video inputs (2 VGA, 2 DVI ,or 1 DVI and 1 VGA).
Take the example of a display that has both VGA and DVI input, and the two computers have graphics cards with different outputs (the first PC with VGA output, the second PC with DVI output).
You can then connect the 2 cables (VGA and DVI) for 2 PCs simultaneously with the same monitor. Then you press the button that changes the "display source" (VGA or DVI) depending on the PC you want to use (see).
Of course this does not solve the problem of having to use double keyboards  and double mouse!

The second method involves the use of a Switch KVM (Keyboard, Video, Mouse), a device that connects a keyboard, a mouse and only a single display, but which has the double output cables ( or triple, etc..) tha connect the PCs to be controlled. The PCs should not be too far apart as the cables are quite short!

They are marketed both mechanical and electronic KVM switch, with different features (VGA, DVI, PS2 or USB keyboard, etc..) also KVM Switch exist for more than two PCs.

PERSONAL EXPERIENCE:
In the first case, the test was done for example with a Samsung SyncMaster 2243WM that has one entry VGA and one DVI, and it works!

In the second case currently I use a KVM switch (mechanical) that allows the use of one keyboard (PS2), one mouse (PS2) and a single display (VGA) connected to 2 PCs.

E-Virus (part I) How to recognize the symptoms of a E-FLU or if your PC has got an E-VIRUS?

E-FLU (Electronic Fluence) and / or E-VIRUS (Electronic Virus) gather all the endless series of softwares that infect the PC by self-replicating and / or consuming its resources (i.e.: malwares, trojan horses, backdoors, spywares, rootkits, dialers, worms, viruses, etc.). 

HOW TO RECOGNIZE THE SYMPTOMS? 

1) The PC is unexpectedly slow: suddenly the speed of execution of any application, even the most banal, it slows down quite sharply. In parallel we see that the hard drive is still active (the LED is constantly lit). The feedback of the mouse or of the keyboard could be slowed. 

2) Problems with the browser: the browser's home page (Internet Explorer, Firefox, Chrome, Opera, etc..) has changed and is pointing to illegal Web sites, or, by opening the browser many pop-up windows appear and replicate indefinitely. 

3) Internet is too slow: suddenly, surfing the Internet has slowed down. 

4) The PC is inoperable: The computer starts but stops immediately with messages like "missing operating system" or "could not find command.com". The PC frequently restarts randomly and unexpectedly. 

5) Modified files: Some files, especially those with the extension. ".exe", ".com", ".dll" have been changed and are larger than usual. The hard drive space has been significantly reduced and / or many new files with unlikely names (such as: yutuewyt.dll, 823746.dll, wuyetur.dll) have appeared. 

6) The antivirus is down: The antivirus will not start functioning as usual and you can not re-install it or install a different one. In some cases you can not even reach the website of the leading antivirus vendors. 

7) New Softwares: new softwares that you have never installed, appear on your desktop or on the tray bar. 

These symptoms, taken individually, do not give you the certainty of the presence of an e-virus in your PC, but they can instill you doubts. Of course, if the symptoms are more than one, the probability of being in presence of an e-virus increases.

More inside: E-Virus (Part II): Maybe your PC is infected by an e-virus... how to verify its presence?

Versione Italiana di questo articolo:
 "E-virus (parte I): Come riconoscere i sintomi di un E-INFLUENZA ovvero quando il nostro PC si è preso un E-VIRUS?"