Sorry DB6, But AST are reknown for their own unique Motherboards and Computer cases. I know of no Socket-7 ( Pentium 200 ) to Socket-370 ( Celeron CPU ) adaptor. If your monitor, Keyboard and mouse are OK, get a quote on a "Box Only" upgrade from a local computer shop which build's it own systems - you are in a better position later when it comes to upgrading as you are using standard industry parts.
Y2K - Bah Humbug!!