Taking a quick look, wp8 has 2 threads running at priority 1. These is not changed even then the normal is pumped up to high, so it's impossible to make a small shortcut setting the priority.
The fix must therefore be done on seti-side...
Taking a look on the latest gui, this is running at priority 2 in background, so even this is too high...
But, depending on number of machines and how often rebooted, you can change the priority on the seti-thread. Atleast one program that can do this in NT is
bvslice
With this, you will atleast manage to set seti to the same priority as wp8, and therefore have a much better chance of success...
If this isn't a solution, you can either try setihide, if this program works, or stop/start the service in the day and only run at night...