The timer job for this operation has been created, but it will fail because the administrative service for this server is not enabled

You get this error when you try to add a wsp into sharepoint using STSADM tool or by doing something similar.
The full error reads something like this:

"The timer job for this operation has been created, but it will fail because the administrative service for this server is not enabled. If the timer job is scheduled to run at a later time, you can run the jobs all at once using stsadm.exe -o execadmsvcjobs. To avoid this problem in the future, enable the Windows SharePoint Services administrative service, or run your operation through the STSADM.exe command line utility."

If you get this, what you need to do is just run this command from commandline having access to stsadm utility like this:

stsadm -o execadmsvcjobs

This will then execute the jobs and all will be well!

Also, in order to stop getting this service related errors, go to the services managment snapin and enable this service: 'Windows SharePoint Services Administration service'