Just keep having problems with 2nd Blog

Hi
I am very new to WordPress but followed a tutorial that enabled me to set up my first blog with no problems. I used WP 2.6.3, downloaded a new theme and it was great. I then wanted to set up my second blog and asked my hosting company how I did this using 2.6.3 – they said they couldn’t support this and suggested I used Fantastico but when I downloaded this it was using WP 2.7 (although it looked nothing like 2.6.3 – it looked old fashioned with the headings down the left hand side with Appearance rather than Design). I couldn’t download a new theme and automatically upgraded (2nd blog only) to 2.7.1. It said it had upgraded OK but now my first blog will not load into my browser although I can access my dashboard through wp-admin. I do feel like giving up on it but can anyone please tell me – 1) what I need to do to get my first blog working again and 2) ideally I would like to set my second blog again using 2.6.3 – so how do I do this? Any help would be greatly appreciated. Thank you