First off, HyperThreading does NOT "turn one processor into two". You still have 2 processors. Second, I get the distinct impression that Vue is not using multithreading to begin with, though I'm uncertain about whether that is due to a limitation of Vue or a setting. That would explain the 50% usage; if it's running single-threaded, then the best case usage it can achieve is 50% of your system. This is further evidenced by the fact that you lost performance with HT on; it can at times hurt single-threaded performance a bit.