We have a large network using a standard XP centrally managed configuration. We have a small number of users who need a 64 bit desktop OS for memory reasons. If we give them Windows Vista machines is there anything we need to especially watch out for when moving our standard profile?
The structure of user profiles changed between Windows 5.x (XP, Server 2003) and Windows 6.x (Vista, Server 2008, 7). The 64-bitness does not affect the user profile structure. Under Windows 5.x, only one folder inside the user profile was clearly made visible to users: "My Documents". All user data was supposed to be stored underneath "My Documents" in subfolders, if necessary. Windows 6.x made the profile folder itself the visible entry point for user data. "My Pictures", "My Videos", and "My Music" were taken out of "My Documents", renamed without the word "My", and made peers of "Documents" under the user profile folder. See the following Microsoft TechNet article for a great description of user profiles, redirected folders, and the differences in structure between Windows XP and Windows Vista: http://technet.microsoft.com/en-us/library/cc766489.aspx.
Your "My Documents" folder can still function as the catch-all user data storage location, and it probably needs to if you are redirecting this folder. The Vista users will just have a bunch of empty folders in their profile, and programs that are written correctly to save to the new locations will save locally instead of under the redirected "Documents" folder. (This may be overridable with Group Policy.)
As far as the user profile as a whole is concerned, Microsoft has changed other parts of the profile structure as well, and my assumption has been that Windows 5.x profiles are not compatible with Windows 6.x profiles. (EDIT: They aren't compatible, but if you follow the instructions in the TechNet article linked above, Vista will apparently keep its roaming profile separate from XP's with a .V2 extension on the profile folder.) I chose not to even try to make this work, and my advice to you is to keep Vista and pre-Vista user profiles completely separate. In my company, when a user gets a new machine with Windows Vista, I rename their roaming profile and manually move all of the documents where they need to be. (You could use Vista's "Windows Easy Transfer" program to migrate settings, but I've never tried it.) Users with Vista on their primary machine may only use XP machines if those machines have Group Policies that are disallowing roaming profiles and offline files. My environment is small, however, and you may not have the luxury of these kinds of restrictions. Best wishes!