I have problem about automatic rename my file such as

original file name as: 20101228.0600.composite.Jet_stream_300mb_model_ove rlays_western_western.x.jpg
20101228.0900.composite.Jet_stream_300mb_model_ove rlays_western_western.x.jpg
20101228.1500.composite.Jet_stream_300mb_model_ove rlays_western_western.x.jpg
.
.
.

programs rename as:
20101228.0600.co-21ab877943ae19ebf97f9591b9c02484
20101228.0900.co-ec560e286781ddf4039c7fa294360376
20101228.1500.co-b30f30e8967dc3b2d033c2e63a77beed
.
.
.

So, I can not rename manually after finished because I download a thousand of files. I need the same file name from original file name.

Please help me setting.