Okay,
I found out how to solve the problem regarding the simulation of telemac2d in parallel. Here is what I've done:
Uninstall previous version of MPICH2
Open an admin command prompt by right-clicking on the command prompt icon and selecting "run as administrator"
Run "msiexec /i mpich2-1.3.2p1-win-ia32.msi" from the admin command prompt to install MPICH2
During installation select that MPICH2 be installed for "Everyone" for all users.
Run wmpiconfig and register my REAL windows login name and password.
To test the execution environment,I've tried to run cpi.exe using: 'mpiexec -n 4 cpi' (in the example folder of MPICH)
And finally I ran a case file of validation folder and everything worked !
But then I tried to run my tomawac case file, but I didn't succeed to make it run... I heard that Tomawac wasn't working very well in parallel mode (version 6.2). Do you think it comes from my installation or from tomawac ?