a program that is running in the background is using authority to take cpu/disk time, when you use an account with no admin privilages, that background program does not have the authority to do it without request. micro stutters stop because you have no background programs taking up your power.
a more indepth view would be: what kind of program wants admin privilages to take up cpu/disk; but when it does not have them, does not ask for them (the normal 'this program requires admin privilages to run' window pop-up request). un-official program installation?
best bet is to create a new account with admin priv's. If the new account is stutter free, then delete your old admin account.
if micro stutters persist then you need to start...