If you want centrally stored user accounts...obviously win2k8 is the way.
However I'm guessing you just want the user's files to be stored centrally... not the settings or anything.
With XP it was simple; just change the location of the My Documents folder to a folder on the network drive... you could do this for each user on each computer such that each user sees the same my documents folder no matter which pc they are on.
With Vista it's slightly more complicated since the User folder contains not just files, but application settings aswell... so it must reside on the local computer unless you are part of a domain. You can however change the location of the individual folders inside the user folder, i.e Documents, Pictures, Downloads, Music... and set their location to a share on the network. You would need to do this for each user account on each computer... so it's not the most practical of solutions, however still pretty un-complicated.
I think the *simplest* way of achieving what you want is to set a network folder to be mounted as a drive each time a user loggs on.
i.e. set drive G: to \\Server\documents\%username%
In vista business/enterprise/ultimate you will need to do it under computer management in the administrator tools.
Simply tell users to save their files there instead of their docments folder.
An alternative is to make a login script .bat file which is executed when each user logs in. You can use this to set the individual directories (Pictures, Downloads, Music...) to folders on your network drive. You can set it to be executed when all users login, which means you don't have to tamper with individual accounts. If you know how to do this... then it's not too hard, if not i'd stick with one of the other two methods.
