What your looking for is something like WordPress MU or WordPress 3.0 when it comes out. You could do multiple installs of WordPress using 2.9.2, changing the table identifer from wp_ to something distinct in each wp-config.php. With 3.0 Mu is being merged into the normal wordpress. What mu/3 will do is allow you to run multiple blogs with one install.
If you go the wp 2.9.2 -> 3.0 situation it won’t recognize each blog when you upgrade, that’s why I suggested MU. Hopefully it’ll notice them all.