Take out the hard drive, then connect it to a USB adapter (IDE/SATA to USB is like $10) and copy it. If you actually want to use the computer, the key precauti

Take out the hard drive, then connect it to a USB adapter (IDE/SATA to USB is like $10) and copy it. If you actually want to use the computer, the key precaution to take is that your device does not have a public IP address. As long as the IP address is something like 192.168.x.x it's probably safe to plug it in. Any viruses on that machine that were active back then are probably still active. Browsing the web at large would probably not be safe at all. Specific known urls like mozilla.org are probably fine. Any defunct software that is running could try to connect to URLs from businesses that have shutdown and had their domain names purchased by a nefarious entity. I would imagine that if you start the device in safe mode, programs won't auto start. I would take out the hard drive, make a copy, delete everything on the hard drive (wouldn't want financial information, old passwords, old authentication tokens, etc. left on it), and then recycle the machine and destroy the hard drive.