Restoring Vista may not remove the BIOS password if that's what it is - so this may not solve the problem (but it is possible it will - I'm not sure but you'll find out if you try it - and it certainly will solve the problem if it is a Windows password).
I'm not suggesting you do the Password process on the XP machine. The process, if you read the entire article, calls for the creation of a Recovery Disk - that disk can be made on an XP machine. Once you have that recovery disk, you boot to it (instead of to the hard drive) on the Vista machine and then follow the password process now that you can access the machine (unless it is a BIOS password which blocks even CD access). If you can't boot to the CD (or any bootable CD), then you'd need to change the BIOS to permit it. If it is a BIOS password, it won't let you in to make the change, but if you can get into BIOS to make the DVD drive first in the boot sequence then it means it probably isn't a BIOS password (though it still may be) and the process has a good chance of success. If the process completes successfully and the problem remains, then it is almost certainly a BIOS password.
I think this is easier (no re-installing updates, no re-installing programs, no resetting configurations and resetting up the network connections and all the other things you'll need to do besides restoring the data), but the choice is yours. If you decide on your process and still have the same problem, then you have no choice but to contact Sony to deal with the BiOS password.
Good luck!