Overwrite the root directory

Hello, i recently took over a site (www.investorsbeyondborders.com

I made a new site temporarily under aboutus.investorsbeyondborders.com

When i instill wordpress using fantastico, i try selecting the ‘investorsbeyondborders.com’ site and it says I cannot install over the root directory. I guess because the original site is found here,

Im wondering how I can remove this and ahve my new site working properly.

thanks,