Hi esm,
Obviously, your a bit new to the XAMPP system...
It's not a very difficult thing to grasp...
The stand-alone Apache server, (which you have as a package with XAMPP) has a folder in it, called htdocs... This is a folder that is accessable by anyone... (providing that they have the permissions/passwords if required)
Xampp has this folder too, and yes, it usually will be located at:
C:/apachefriends/xampp/htdocs
In there there will be your folder, catalog.
(This is where you should have ftp'd your OScommerce template/system...)
In your webbrowser, you should point it to
http://localhost/catalog/
if a list of folders opens, click on the file that says something similar to index.php... (sorry i don't have OScommerce, so i don't know what it's called...) If it has been installed properly, a website should open, usually with configuration instructions... You SHOULD be able to handle it from there...
If not, open the original download file from the OScommerce website,
and try and find a folder called docs, documentation, instructions, or help.
There should be some very basic installation files in there, and you can start again properly...
Hopefully this will help... maybe not...
Once I was told (by a bunch of people on a dodgy forum) that if you can't install it, it's probably too far out of your league, this might be right, but things can't be that hard to install... Ever...
Hope this helps, and I hope that things install/configure properly...
God Bless,
Mitch