Problems importing latex documents

[Jose]

Hi, I have always had this problem, could someone explain me how I have 
to import a latex file to lyx.  I have always tried with import latex 
but it gives me the following error:

Cannot convert file

Error while executing
reLyX -f 'vvv.tex'
and thats is all.  What should I do.  That is when I am using windows

Regards

Jose