[CentOS] yum/RPM Problem: several packages with the same name were installed, how to remove one of them ?

Hi,

We have a cluster with CentOS 5.5 installed with oscar. The firm which
has pre-installed the cluster has  done strange things...and now I get
problems:

- if I understand correctly what was done, several infiniband CentOS
packages were installed (compat-dapl, compat-dapl-devel,
compat-dapl-utils, libibcm, libibverb, librdmacm, mpi-selector).
- Then the tar package from OFED was installed. This archive contains
rpm packages too...and were installed.
- So on our nodes we have several versions of "compat-dapl,
compat-dapl-devel, compat-dapl-utils, libibcm, libibverb, librdmacm,
mpi-selector".

I would like to remove the package from CentOS (in order to have homogen
OFED environment). How can I do that ?

These packages target the sames files...If I remove the package of
CentOS, will it erase all the files in common ? how does rpm/yum behave
in this situation ?

Best regards,
Guillaume