Due to the performance hit after installing Solid Edge ST7, the client decide to downgrade their installation to Solid Edge ST4.
Solid Edge ST4 does not support opening NX9.prt, so is there any workaround for that?
No! ST4 was earlier released than NX9. Only way (what I know), He has to export his NX files into parasolid (V24 or earlier) or other file formats...