How many times can I reinstall SQL Server 2008 using the same product key

If you upgrade you will not be able to (with ease) move a database from 2008 back to 2005.

Like lynnroth, I run multiple instances (05 standard, 08 dev, and a 05 express instance) for testing specific things.

If you're worried about backwards comptible SQL you can use various compatibility level values. It's not exactly like running the SQL against a different version of SQL Server, but it makes migrating from version to version easier.

Also, to note. You can only have one default instance of SQL Server on a machine (machinename). I find it easier to manage which version I'm on by naming the instances accordingly...

machineName - default (used the most)

machineName\SQLEXPRESS (sql express' default instance name)

machineName\SQL2008 - 2008

Don't forget that running databases against multiple instances is different resource-wise than running all databases against a single instance.

Kris

1) Yes. You will need an Active Directory infrastructure available. SCOM is heavily tied into those services. It is described further in the Infrastructure section of the Environmental Prerequisites.

2) Yes, but you may need a newer version of SCOM 2007. The original release version of SCOM does not support SQL 2008 because it didn't exist when it came out. However, SCOM 2007 R2 does support SQL 2008 with SP1. Here is the Operations Manager 2007 R2 Supported Configurations page. I think SCOM 2007 SP1 also supports SQL 2008, but you should just start with R2 if you're starting from scratch anyways.

3) Install Active Directory and get media for SCOM 2007 R2 instead of the original release.