2 domain instalations cant access one

I think I screwd up! I installed wp 2 days ago on a domain and then installed it on to another deferent domain both hosted at host gator using fantastico. I was able to select the new instalation domain from a dropdown list within wp. All was good until i enterd the exact same user/login password info that I used with the first install. Now I cant access the first wp instalation. when i login it takes me to the new install. I thought I would be able to select the domain names I was working on in wp. Any ideas? Thanks, Bill