Lately there has been many upgrades of NAV-runtime since customers are upgrading their PC:s to Windows 7. There's usually no big deal to upgrade only the run-time enviroment but keep in mind that it's not supported by Microsoft if You should run into problems, so do Your testing before doing it on a production database.
One thing the customer often ask is how to use those new Office buttoms. So here's a couple of tips if You wan't to start using stylesheets after the upgrade.
You will need a couple of objects from the new version. Open up a NAV 2009-database and export these objects:
Import the objects into the old database and copy these three functions from codeunit 1 in NAV 2009 into codeunit 1 in the old database.
Restart the client and copy all three rows in table 200000006 in the 2009-database and paste them into the same table in the old database.
The only thing that's left to do now is to export and import the stylesheets one by one. Choose "Style Sheets common to all forms" both when exporting and importing.
If You want to build Your own style sheets You must download and install the Style Sheet Tool. Version 2.0 can be downloaded from here and here's an update that add's some new functionality.