If I'm not mistaken, renaming them will not work. XP will some how know they have changed and create new profiles named steven.domain1.000 and steven.domain2.000.
Your better solution is to create 1 or 2 local profiles and use XP's profile copy routine. (IE: Right Click my computer, properties, Advanced Tab, Profiles) and copy domain1 to a temp local profile and domain2 to a different local profile. Then, copy the temporary domain1 over the permanent domain2 and vice versa. The reason for making backup copies of both are just in case... Also, the reason you use a local profile is that way the copy routine can see the profile and doesn't tag it as unknown because of the domain security.
In order to get the profiles to copy smoothly you need to reboot the computer and login as an administrator of the local box. If you fail to reboot, they won't copy as there will still be files left open. Even a logoff does not close all the open files.
This is the solution we use when we have computers jumping domains.
Renaming the folders will NOT work as they are associated with SID's in the Registry, and you will have all sorts of issues with it. Try using the File and Settings Transfer Wizard to copy your profiles. Log in as the old user, launch the F&STW (Start-Accessories-System Tools), and run the wizard as if you were on the 'old computer', but save the settings to a folder like c:oldusersettings. Then, log in as the new domain user, and run the F&STW as if you were on the 'new computer', and specifiy the c:oldusersettings folder for the location of the data.