Nios 2 modelsim simulation

Hi,

when I try to do a simulation in Modelsim with Nios2.... starting from Run as -> Nios 2 ModelSim I see this messages in ModelSim Transcript Window:

# vsim -gui DE4_SOPC_sim.mpf

# ** Error: (vsim-19) Failed to access library 'DE4_SOPC_sim' at "DE4_SOPC_sim".

# No such file or directory. (errno = ENOENT)

# Error loading design

do you know what error is ???