The conclusive method to make sure there aren't any viruses present on a computer is to reformat the computer's hard drive, which erases everything on the drive, and then load a fresh operating system. Thereafter, be assiduous about installing software updates and careful about net connection and security. The ongoing tasks will be simple for Rad and me as this computer would be used only to run the GS-911 software, and would not be used for email or browsing the web.
A new operating system is installed on the computer's hard drive using an installer program; the installer is usually contained on a DVD inserted in the computer's DVD drive. (Some current computers download their OS from the manufacturers' websites, or maintain a separate part of the computer's internal hard drive that contains an OS installer.)
Windows XP -> Windows 7
The NC4200 came with the Windows XP operating system already installed. My friend had an unopened retail-package Windows 7, a more recent OS, that he'd bought for a computer now long gone; he contributed it to the project. Having to buy an OS would of course have increased our cost; as I write this, Amazon sells Windows 7 for $89.
Loading the Windows 7 Installer
The first task was to load the Windows 7 installer into the new computer; the installer would reformat the NC4200's hard drive and install the fresh operating system. Reformatting the drive required the computer to start up ("boot") from the external DVD drive. With the computer off and after making sure the Windows 7 DVD was in the external DVD drive and that the drive was plugged into the NC4200's powered USB port, I turned the computer on. The external drive spun up and the screen displayed "To boot from an external DVD drive, press any key." I pressed and held the "a" key until the computer acknowledged with a beep, then I released the key. Windows loaded a lot of files...slowly...with a thermometer across the bottom of the screen indicating progress. Finally, the Windows 7 installer appeared on the screen.
Reformatting the Hard Drive and Loading Windows 7
Reformatting the hard drive and installing a fresh OS are both done by the Windows 7 installer. The screen prompts are easy to follow. One must specifically direct that the hard drive be reformatted: when the installer screen asks "Which type of installation do you want?" select "Custom." The installer screen will then ask "Where do you want to Install Windows?" Respond by clicking on "Drive Options," then select "Format."
Reformatting a drive erases all the data on the drive. To protect user files and prevent their inadvertent erasure, installers don't make it easy to reformat a hard drive - many warnings are given, and the user must several times confirm that reformatting will completely erase all information on the drive. I didn't have any data on the drive, and to ensure there were no viruses, did want the drive erased and reformatted. The OS installation also required that I enter the Microsoft product key provided with the retail package DVD, to verify that the software was legitimate and legal.
After the installation was complete, I shut the computer off and disconnected the DVD drive. Then I turned it on again, checking to see that the computer booted Windows 7 from the internal hard drive. It did.
OS Updating and Wi-Fi Challenges
Making sure the OS was updated was next; updating is accomplished by connecting the computer to Microsoft's update servers on the net. I wanted the computer's wi-fi operable, to connect to our local network and the net; in our use, an Ethernet (cable) connection would be very inconvenient. This did not go well: following the directions in Windows 7's help files led to a dead end - the computer did not display a wi-fi icon and thus would not connect to my available wi-fi network; in fact, no networks appeared. Further, the OS's Device Manager, one of the computer's Control Panels that shows what hardware is present, didn't show the presence of the necessary hardware, a wi-fi networking card.
With some web searching, I learned that Windows 7 was introduced several years after the NC4200 computer was first sold, and that H-P never provided drivers for Windows 7 - "drivers" are small bits of computer code that enable the CPU to talk to the hardware. With no drivers, wi-fi with Windows 7 on this computer appeared to be a non-starter.