After selecting the option to create a new preboot environment, it may take up to half an hour for Bootwiz.exe to run, and then another 20 minutes or so to create each preboot environment. In my limited experience, it is best to create only ONE preboot environment at a time, wait for it to be created, then create the next, etc.
You can force Bootwiz to run faster on the server by going to the SMA client on your PXE server, going to Settings, then Send a basic inventory and Update the configuration. Have Task Manager opened at the same time - you should see bootwiz.exe kick off. Once it's completed, you'll know your environments are created. It should also clean up those old entries.
I've just had a problem where it took bootwiz over three HOURS to create a new entry. It was hung up on something, but it eventually caught up. One thing you can try is to create one more final preboot entry, a temporary one you can delete later, just to make sure the bootwiz.exe process is kicking off.
Also, there's a bootwiz.log located at C:\Program Files\Altiris\Altiris Agent\Agents\Deployment\Task Handler\bootwiz on your server; that might have some more helpful information in there. Or... it may just confuse the heck out of you, hehe.