Hello,
Well basically when manually copying products accross from an existing system I was entering weights wrong so I needed a quick way to update them all so me and Phil Richardson (a friend of mine) build this simply script. Simply correct the details at the top of the file for your database and the MD5 password and then upload and run in your X-Cart root dir.
And here it is :-
http://www.craigbrass.net/xcart/weight_updator.zip
Best Regards,
Craig Brass