sql server standard and sql server enterprise editions are designed to install on server OS's. However, SQL Server Developer edition runs just fine on my windows xp with sp2 laptop.
the developer edition is exactly like SQL Std and Ent in tools looks and function. it is just limited in its client support. somewhere around 8 clients i believe.
on a side note, i worked on a really slow sql server once and found out that they had installed the dev edition on a production server.......
pop the cd in
finished in 2 minutes. that'll be $100.00 please