Anti-virus for Windows 2000 Server SP4

I need a GOOD anti-virus that will run on Windows 2000 Server SP4. I am doing virus removal on my ex-husband’s Toshiba Tecro8000 laptop with a 10gb drive. He only uses it on the jobsite, and he’s not at ALL technical. He uses the laptop to check emails and surf the web. No video, no music, no downloads.

Due to disk size limitations, and issues with other programs such as upgrading BIOS - I don’t really want to upgrade him to XP.

Is there any good antivirus programs that will run in this situation? Even though I swear by Comodo Firewall, I’ve only used Avast for the simplicity, especially for novice users.