_[DH]_ spotted a problem here. The SPR register is specified by 7 bits, so there can only be 128 registers. As you said, the register $0 (SPR[0]) is a dummy SPR register and the rest ($1 to $127) are _normal_ SPR registers. So in the end we have: 1 dummy SPR register ($0) + 127 _normal_ SPR registers = 128 SPR registers

So the necessary changes are in the first line:
<i>&nbsp;&nbsp;&nbsp;&nbsp;static const wxString spu_specialreg_name [128] = {</i>
and in the last line:
<i>&nbsp;&nbsp;&nbsp;&nbsp;"$120", "$121", "$122", "$123", "$124", "$125", "$126", "$127", "$128"</i>