Microsoft Excel 10 | Open files in different instances per default

Create a reg file and add the following stuff:

[HKEY_CLASSES_ROOT\Excel.Sheet.8\shell\Open\command]
@="\"C:\\Program Files (x86)\\Microsoft Office\\Office14\\EXCEL.EXE\" /e \"%1\""
"orig"="\"C:\\Program Files (x86)\\Microsoft Office\\Office14\\EXCEL.EXE\" /dde"
"command.depr"=hex(7):78,00,62,00,27,00,42,00,56,00,66,00,21,00,21,00,21,00,21,\
  00,21,00,21,00,21,00,21,00,21,00,4d,00,4b,00,4b,00,53,00,6b,00,45,00,58,00,\
  43,00,45,00,4c,00,46,00,69,00,6c,00,65,00,73,00,3e,00,56,00,69,00,6a,00,71,\
  00,42,00,6f,00,66,00,28,00,59,00,38,00,27,00,77,00,21,00,46,00,49,00,64,00,\
  31,00,67,00,4c,00,51,00,20,00,2f,00,64,00,64,00,65,00,00,00,00,00
"command"=-

[HKEY_CLASSES_ROOT\Excel.Sheet.8\shell\Open\ddeexec.depr]
@="[open(\"%1\")]"
"orig"="[open(\"%1\")]"

[HKEY_CLASSES_ROOT\Excel.Sheet.8\shell\Open\ddeexec.depr\application]
@="Excel"

[HKEY_CLASSES_ROOT\Excel.Sheet.8\shell\Open\ddeexec.depr\topic]
@="system"

[-HKEY_CLASSES_ROOT\Excel.Sheet.8\shell\Open\ddeexec]

[HKEY_CLASSES_ROOT\Excel.Sheet.12\shell\Open\command]
@="\"C:\\Program Files (x86)\\Microsoft Office\\Office14\\EXCEL.EXE\" /e \"%1\""
"orig"="\"C:\\Program Files (x86)\\Microsoft Office\\Office14\\EXCEL.EXE\" /dde"
"command.depr"=hex(7):78,00,62,00,27,00,42,00,56,00,66,00,21,00,21,00,21,00,21,\
  00,21,00,21,00,21,00,21,00,21,00,4d,00,4b,00,4b,00,53,00,6b,00,45,00,58,00,\
  43,00,45,00,4c,00,46,00,69,00,6c,00,65,00,73,00,3e,00,56,00,69,00,6a,00,71,\
  00,42,00,6f,00,66,00,28,00,59,00,38,00,27,00,77,00,21,00,46,00,49,00,64,00,\
  31,00,67,00,4c,00,51,00,20,00,2f,00,64,00,64,00,65,00,00,00,00,00
"command"=-