Upgrading Window Server OS; What is the impact on Siebel software?

Hi,

Siebel Services & Apps involved in this question are;

1. Siebel Web services (for DEV environment, the Siebel version is Siebel 8.1.1.2)
2. Siebel Tools 8.1 (used in all environments)

-We have to upgrade the Windows Server OS of one of our DEV server from the currently used Window Server 2003 to Windows Server 2008 R2.

-This server currently has Siebel Web services and Siebel Tools 8.1 installed and running.

-The Window OS is in C: partition while all the Siebel Software is in partition.

-If we upgrade the Window OS on C: partition, what are the preparation that you would advise us to do for Siebel in order for it to work and run normally after the OS upgrade?