I download this Rover software,burn end anything happens,reports that it is not good cd...

The file is good - I used it.

So either
1) you have not followed the instructions correctly
2) you are already on the latest firmware
3) your nav unit is broken

Can I go to some older firmware..??

certainly - try google

I got the original CD software from Range Rover, but nothing has changed,again appears that the CD is not good, whether it is possible that corrupt laser and therefore do not read software.

then the RR Mk3 may have a bad laser or corrupt flash.

Send to VDO Wetzlar Germany for repair, or replace with another Mk3 or Mk4.