You sure can do this, using the Attribute Wizard in Essentials (in the Authoring space). You'll need to right click Attributes node, and create a new attribute based on the 'Windows Operating System'.

If you are only interested in clients or servers, you could instead base your attribute on 'Windows Server Operating System' or 'Windows Client Operating System'.

When you get to the spot in the wizard where you choose WMI or Registry, choose WMI.

• Namespace is root\cimv2.
• Query: Select name from Win32_Processor

for criteria, you want to match on Name 'Contains; Celeron or Name matches wildcard *Celeron*

There is a nice step-by-step on MS TechNet site (link below), but if you get stuck, just let us know and we'll help you through it

How to Create a Custom Attribute in Operations Manager 2007

Good Luck!

 Couple of things that may help you when working with your custom attribute in SCOM

The New Attribute wizard results in a custom class being created, so you can do two things to see the value of your new class.

• Create a new State View and  change the target from the default (Entity) to the name of your attribute created in the wizard.
• Use the Discovered Inventory view in the Monitoring space, click Change Target and select your class from the list.

Create your custom attributes in their own management pack. You cannot delete a custom attribute through the Operations console UI, so isolating this to it's own management pack will be best. 

If anything remains unclear or you've not yet met with success, just let us know.

Remember this WMI query will run locally on each of your agent managed systems. If you want to know if your query is correct, run the query on a System with a Celeron processor. That will tell the story. If you've created the attribute in a custom management pack, you could also export the management pack so we can look at your attribute definition and query.