Converting wmv to play on Sony Ericsson P910i

I have a short video/audio clip that I can play on with an extension .wmv that I want to load to my mobile telephone a Sony Ericsson P910i but when I try to copy it to the phone memory there is a message that reads “the file typr is not allowed in the destination folder” - anybody out there can advise?

P910i Can’t supportWMV Files....U can convert it to RM...Is Nice oso...

wat is “rm”? n were do i get the program from?
which addy? thanks

Using winAVI converter....all file can convert.Good luck.