If you know what you are doing and want to mix and match components and know how to sort out any conflicts, it's worth it. But, to get the most out the new CPU, you would undoubtedly need a new AGP video card, a DVD drive, 40Gb+ HDD etc - as well as the new PC2100 memory.
If not, you are better off buying a new machine off the shelf from someone like Dell. It will all work together and have a full warranty and will be cheaper than you buying all the parts and putting them together (they get a lot better price on the parts than you do!!).
Any remaining components in your 266 are probably reaching the end of their life anyway. Give it a ceremonial funeral in the nearest skip.
[ 23 February 2002: Message edited by: ORAC ]</p>