How do I get the center screen on PMDGs 737-700 to work?It

Tony,It will only work with the 800/900 update. With that you will however get the upper/lower DUs working for all your NGs.

Thanks so much.I

The 800/900 added some fairly significant functionality and modifications to the product. You can get the specific list from the PMDG web site or try doing a search here in the forum.IMHO it is worth the additional investment, but my opinion may be a bit bias. ;-)