Pentium 4 HT 530 is basically a Pentium 4 3.0GHZ but with Hyper-Threading technology support. It still has only one core but the Hyper-Threading allows it to perform multiple tasks as if there's more than one core doing the work. This obviously doesn't affect today's games as a single 3.0GHZ core even with HT isn't, most probably, enough to handle today's games at high settings.
Compared to the original Pentium 4 3.0GHZ the performance is significantly better but the Prescott architecture is one of intel's worst and the performance may hinder due to overheating issues.