Total Newbi Question

Hi I was looking at upgrading my system

I have an Athlon Xp 1800

The Processor that was recommended (or the only thing they have) by the store was an Amd Thoroughbred my current motherboard (I believe thats right) is running a 266MHZ Bus

The Processor I was planning on buying was the thoroughbred 2400 to support my motherboard 266 bus

My question is are these AMD thoroughbred processers compatible with my motherboard

And are they better than the Athlon XP are they the same thing or what

My mother board is an AK31 Socket A Spacewalker mainboard

It says in my motherboard manual that it will support Socket 462 package CPU with 200/266 MHZ FSB

Can someone help me out

I am sorry If this is a dumb question

Cheers