Wow - lots of good advice.  I decided to pre-order PRO 2012 based on what you you've said and what I've read.  I am a newbie and can use all the help I can get, so if Pro 2012 can help do that better than Poser 9, that is well worth the investment. 

Thanks everyone for your insights. I'm anxious to get my hands on it to begin playing with it. I hope its not full of bugs.

thanks everyone for the advice. I really do appreciate it.

I would add...

I would either upgrade to a larger drive (you can get 2T and 3T 7200RPM SATA 6Gb/s internal drives for under $200 now) or, if you have a free drive bay, add an internal drive and direct the install to that drive.  I would never install an application to external drives. I might save my rendered files there, but never executables.

Unless you have a solid Windows admin background, I would highly discourage you deviate in anyway from the standard installation. You can override the default installation location during the install of course, but if you are thinking about moving runtimes around after install, you are just asking for trouble. Windows expects things to stay where they are put during install. This is not Linux, Unix or MAC OS - this is Windows, and Windows is not forgiving. The Windows registery records all sorts of install information, including file path locations of binaries. So if you change up things such that the registery info is not in synch with where it thinks things should be, you can very easily corrupt the installation and the software will not work at all.

If you are concerned about drive space, you could during install, tell it to install the software to your external drive, but this also is risky unless the external drive is always connected to the PC and the Drive Letter assigned to it does not ever change. Windows often loads pieces of various software during boot up. If Windows can't find these pieces because the drive is not attached or is not associated to the drive letter as it expects (the registery has this info), then it is possible Windows may not even start up correctly and you might have to reinstall Windows.  

The other thing to consider is the speed of the drive and how you connect it to the PC - Poser and other IO intensive software need ability to read and write to disk fast. If you connect an external SATA drive to the PC via an eSATA connection, no worries since the speed communicating to the drive is the same as if it was an internal. On the other hand, if the external drive is connected via USB 2.0, the communication speed to the drive will be MUCH slower compared to if the drive was internal and may negatively affect performance of your program during read/write operations.  Firewire is considerably faster than USB, but still is not at bus speed which an internal drive would operate.  So, if you can, it is best to install render intensive software on internal drives, or via eSata external. It is highly discouraged to use external USB drives for this purpose. They make good places to store backups, documents, photos, music, and perhaps video. They are not good for applications where decent IO rates are needed.

Quote - My sons PC is ready for the Pro 2012 upgrade in a couple of days. This time around we are going to put the runtime folder on an external hard drive, and I have some questions before I mess that up.

Should I set up a folder called "poser" on the hard drive for the new runtime folder, or is it better to let Poser do all that when installing? Also, is there a way to stop the external hard drive name letters from changing? I have three external USB drives and occasionally the drive letters change, and I know that will cause problems down the road.

Anything else I should be aware of with external runtime? Please let me know so I am armed in advance. A few nuggets of information are worth more than a mountain of ignorance.