I've also got to work on a Win7 x64 machine...
I've installed BOINC as a single-user app for an administrative user account. I'm logging in as a plain user, starting BOINC manager as this admin. So far so good, everything seems to work fine including GPU computing and app graphics. Then I've installed TThrottle and started it as a plain user (well, I've made the BOINC data folders readable for me). TTh was running fine, but upon an attempt to throttle applications, nothing happened with them (as Yeti observed, they continued to run on 100%) and TTh was using one complete core in "red mode" (spending a lot of time (80-100%) in system calls). I suppose the driver is probably not used for tthrottling, just for temperature readout?
After starting TTh as an admin, it is able to throttle BOINC applications and runs "pretty silently". Just to solve the automatic startup "as an admin" (possibly with some link), often it happens that I start it as a plain user process and it is then hungry...
A side note: This damned Win
Home system has a drawback, that lusrmgr.msc ("
Local Users and Groups") refuses to start ("not allowed") and I do not know how to add someone to
boinc_users and/or
boinc_admins groups

. Is there any commandline/graphical program capable of doing this here? BOINC installer could happily handle a couple of user groups... Or could please someone point me to any MSDN doc how to do this programatically?