Dragon NaturallySpeaking and speech recognition in general is one of the most processor intensive programs on the market, it uses sophisticated acoustic and language models to interpret your speech and turn it into text.  Users will simply not be happy using Dragon NaturallySpeaking on a computer that is less than a Pentium IV 1 GHz with 256 MB of RAM.   This is especially true if you plan to dictate directly into a Microsoft product, i.e., MS Word or a Corel Product, i.e., WordPerfect.  The software will work on slower systems however, it will run s--l--o--w.   The easiest most cost effective way to upgrade a system is adding more RAM.  For new computer purchases I recommend a Pentium IV 2-GHz with 1024 MB of RAM for any computer system running NaturallySpeaking Professional, Legal or Medical.