I used to ask myself , Where exactly are sharepoint documents stored ?
hmm may be on the file system ? no ! Not reasonable..
In the content database ? hmm
After investigating this subject, I found out that every time you save a document in the document library on a SharePoint site, the entire contents of the document is saved in binary format in a single image-type field in the SharePoint database.
WOW, an entire document in a single field ??
When I told a colleague about that he asked me for an evidence.
Ok !
Guys, check this link : http://msdn.microsoft.com/en-us/library/ms998690.aspx , documentation on the Microsoft Developer Network always says the truth 🙂
Ayman El-Hattab's Technology Blog 
Good information.This is all woinrkg for me, but I would like to find a solution for one thing. If a document has been copied previously into the library that I have my send to copying into then I get an error, ( Copying to the destination did not complete successfully ) when I try to do a send to the second time. Because of an existing work flow and attempting to keep things as simple as possible for the user, I need them to be able to just select the send to option and replace the existing copy. Do you know if there is anyway to get past the error when attempting to send to an existing file?Thanks in advance