Dual-Boot / Second Drive: Install Windows 10/11 LTSC or Linux (Mint, Pop!_OS, Bazzite) alongside.
Hardware Upgrade: Any CPU from 2012+ (Sandy Bridge / Zen 1) + 8 GB RAM + SSD + GTX 1050/RX 570 = plays 90% of games at 1080p.
Cloud Gaming: GeForce Now, Xbox Cloud, or Boosteroid stream to a browser on Windows 2000 — but Windows 2000 browsers (Firefox 12, Chrome 49) are too old for modern web DRM.
Recommendation: Retire the Windows 2000 machine for offline retro use only. Build or buy a modern system for current games.