Hello everybody.
One question for you: Do I have to create a subdomain for locating all the files from the localhost in the client's web server.... or Can I locate the files just in a folder named htdoc or xoops?.....

What are the best recomendationes to do it?...Every thing works great at my localhost and I don't want to lose any thing...(I already checked the information in the forum at the link:

[size=x-small]https://xoops.org/modules/newbb/viewtopic.php?topic_id=20863&forum=7&post_id=90497#forumpost90497[/size]

Thanks in advanced!!!

If your clients site is for example: http://www.myclient.com then you can place your XOOPS site directly in the root. Depending on your server configuration it can be called htdoc, public_html, etc.
Pro's: shorter url's
If you prefer you can create a folder called XOOPS and place your instalation there.
Pro's: by having an aditional index.html in your root you can further expand the website beyond xoops, for example, have a part in flash and another in xoops.
Con's: This method, beside's having longer url's also adds a further degree on complexity to the site.
If your client will only run XOOPS (which can pretty much handle the vast majority of tasks) then I would advise placing your XOOPS instaltion in the root, that way when sometime types http://www.myclient.com XOOPS appears.