Is there a way using boot media to get an existing windows server to install an SCCM Client and complete a task sequence? Is this supported?

What do you want to do exactly? Install the CM client on an existing server? And then? Run the part of a task sequence that would be executed after "Setup Windows and ConfigMgr"?  Or run a (OSD/non-OSD) TS at all? I don't get the exact scenario. 

Hi Torsten thanks for the reply.

My requirements are as follows:

Existing Windows Server, Install the SCCM agent, Deploy our Standard Applications as quickly as possible.

To expand on the requirements, our organisation acquires other companies which have existing infrastructure and I can just install the SCCM agent on them and have them join default collections that push out our standard applications, but the time before the agent reports back to SCCM and actually starts deploying our standard software is anywhere from 1.5 to 8 hours. I need the default applications to be installed more quickly than this. I have been trying various things, and none of them bring the time to install the software down below 1.5 hours. So one way we could do this is to run a task sequence that will install the Agent and install default applications.

Does that make sense?

The SCCM agent will need to be running on the server before a task sequence can be run. Have you tried to force the SCCM machine policy after the agent is installed?

1.5 hours does seem a long time for an machine to register in SCCM and get a deployment. There could be a few reasons holding things up, the collection membership evaluation or the SCCM agent installation switches. 

The only switches we are specifying are the /MP and SiteCode. Should we be specifying anything more?

That should be fine. A clients sends inventory and pulls policies as soon as it is installed, so you have to find out where the delay comes from. Any chance that it takes a while until it is member of the collection(s) where the software is targeted to? Or that discovery has to run before that happens?

The server is a member of the collection, I have a separate process that ensures that that happens and it takes about 5 minutes to update. even when manually attempting new machine policy refreshes it takes quite a while to start reporting.

Your SCCM hierarchy structure, if you have a CAS or secondarys, could cauase a slight delay in clients getting policy.

Check which MP the client is contacting and ensure that the MP is functioning at efficient levels. Outboxes are not clogged up - the outboxmon.log will show any issues.

We have a CAS and 2 primary sites, but checking the outboxmon.log nothing seems to be wrong on both the MP in the primary site and on the CAS.

And I agree that there could be some delays, but the time its taking is way over what I would expect.