Hum... Restarting Apache should cause it to load 4.3 and dump 4.2.3. By "info window," I'm guessing you mean the output from phpinfo()?
Can you run "php -v" and make sure it reports 4.3 as the version number? If not, maybe something didn't work correctly for the install. This checks the CLI and not the Apache module, but if the CLI didn't get installed, then this would be an indication of a bigger (non-Apache specific) issue.
Also, try checking the Apache error_log to see if it reported an error message.