I believe the m848a uses the AGP slot for video cards. At one time that was the "Bee's Knees". A dedictaed slot for the video card. Now, I suggest you give up and get a new PC. I had a lot of hassle trying to get such a card to perform well. That said I admit I had been running Windows 7, if you have XP you may achieve more since the PC I was upgrading seemed to do better with XP anyway.
But ultimately it depends on what you want to do with it I suppose. I'd suspect most things could cope with playing youtube video. But I don't believe you are giving yourself an easy job. If you really must use this PC I'd suggest going for an AGP compatible video card with as much video memory on it as you can find.