I'm afraid that a simple copy/move is not gonna work, because the settings in the database of oscommerce will still refer to the old location, the subdirectory.
I suggest you download the subdirectory (your site), with an ftp client. Then, go into that subdirectory on your local drive and upload everything in there to the root directory, then you should be able to access your admin (still the one in the subdirectory), and change your settings there so that the install path refers to the root directory instead of the subdirectory. Right after you made that change the admin in the subdirectory won't work anymore. So exit from it. After the change has been saved to the database, only the admin in the root will work.
Then test your site in root and if everything works, you can just delete the subdirectory. A bit more complicated - or rather: it takes a bit longer to download and upload everything - but at least then you can change your settings easily.
Otherwise you end up with your files where you want them but a non working site.
Edited by xmephistox, 07 June 2010 - 11:02 PM.