Help w/ running nopCommerce locally.

hi, i've been playing w/ nopCommerce and i like it very much ... i've been messing w/ the looking fields by modifying the .css files.  Most of the time, i update the files, then ftp to my godaddy.
I'm learning .net so i want to mess w/ the actual .cs code but i'm not sure where to begin, I downloaded the whole packages from nopCommerce, with source codes everything, currently on my pc, i've sql server 2008/sql Express, and Visual Studio installed ...
i tried http://localhost/nopcommerce/default.aspx after download, but it show an error message (Configuration Error - web.config line 4) ...
Could someone please show me the steps so i can modify the codes, compile, then upload?

thank you very much,

please :-)

solution must be opened with VISUAL STUDIO - cannot be opened with visual web developer
select open PROJECT
select  NopCommerce.sln
right click NopCommerceStore
select view in browser

i'm using visual developer express, tried to open the solution file, but then get the box: "Solution folders are not supported in this version of the application.  Solution folder 'Dependencies' will be displayed as unavailable."

Same thing for the other folders: Payment, shipping, tax, Libraries ...
after clicking OK on those messages, it started to load for a while, then show "Some of the properties associated with the solution could not be read."