Is there software for overclocking an Intel Pentium 4 HT Processer?

You won't manage to overclock a Dell. With any computer, software-based overclocking is chancy at best. Overclocking is 1. a skill best left to experts, unless you don't mind breaking some hardware along the way 2. best done with specific hardware selected for its performance and overclockability and 3. not the best way of getting extra performance out of your aging Dell. Like the other folks said, upgrade to 2gb of RAM (use crucial.com to check what speed you need) and you'll see a world of difference.