Do not do this. Although the database names are the same and the structures similar, the AD entries are not and you risk corrupting your AD. When restoring always restore onto the same version of Exchange. Also make sure that the databases sit on the same drives. The location of databases is stored in the AD and not in Exchange. There is a Microsoft white paper on replacing Exchange server hardware that is very useful.
If you want improved performance for your server you can install Windows 2000 Advanced Server which will allow you to use more than two processor and 2GB of RAM (if you set the /3GB switch in boot.ini)