mc707: well, both
NtQueryInformationProcess and
ZwYieldExecution APIs are just kind of toys for "casual" market (like protectors developers). The hardcore ones are still behind the official knowledge
I am talking about anti-debug methods theoretically not possible to skip. The only metod to skip them is to write own software emulator (like VMWare) with wide CPU emulation ability. Debugger detections like XProtector and Starforce have are still toys (althought XP and SF debugger detection doesn't play so important role - even if you deal with it there is significant decompilation work to perform).
Ehh... these are topics for another threads..
Good luck.