Net Defender, a game where you fight viruses and malware using protection software, but you are the protection software protecting the computer.
The first level is just a Tower Defense style game, use the mouse to click and place towers and phasers to kill the viruses and malware.
The second level is a platformer with blasters to kill the malware hiding in the packets.
This will switch and get slightly harder over time.
The included file will just be an executable that runs the game without installing.
To go in full screen use Alt + Enter.