That's still a pretty old computer, bro. Most computers these days come standard with at least a couple of gigs of RAM, but it SHOULD be able to run Combat Evolved. Minimum requirements are
* Operating System: Microsoft Windows 98, Microsoft Windows Second Edition, Microsoft Windows Millennium Edition (Me), Microsoft Windows 2000, or Microsoft Windows XP.
* Computer/Processor: 733 megahertz (MHz) processor.
* DirectX: DirectX® 9.0 or later. (DirectX 9.0b is installed by Halo.)
* Memory: 128 megabytes (MB) of RAM.
* Hard Disk: 1.2 gigabytes (GB) of free hard disk space.
* Video card: 32 MB with 3D Transform and Lighting capable.
* CD: 8X.
* Sound: Sound card, speakers, or headphones with multiplayer play.
* *56.6 Kilobytes per second (KBps) modem or 10 MB network adapter. Multiplayer servers require broadband to run a server.
* *Additionally, you must have an Internet Service provider (ISP) or a Local Area Network (LAN), if you want to play multi-player games
So yeah. It also says you may have graphical issues if you have an unsupported graphics card. So if you have some onboard POS card, I would run in safe mode, but I think it's time to upgrade. Hope this helps, check out the source for more details about the video problems.