Do you mean you can't open the RAR file or that you can't open the Maya file within it?

If it's the RAR file your having trouble with then you need to download a program such as WinRar or WinZip and extract the folders from the RAR file.

If you have done this but are having problems opening the Maya file it may be because you have a different version of Maya to the one it was made in.

If this is the case then you can open the file and change the version number to whatever number your Maya is. There should be a couple of references to the version number on the top line.

Hope this is what you were after.

Chris