Svchost is what manages running services on your computer. Usually there are several instances of it running. Shutting enough of them down will lock your OS up and then you have no choice but to "pull the plug out of the wall" to even shut the PC down.
Download the Adobe Flash Player installer directly by right clicking one (or both) of the following links. Choose "Save target as" (IE) or "Save link as" (Other browsers).
Reboot, so nothing but Windows is running. THEN go to your downloads folder and double click the appropriate installer to run it.