WordPress upgrade problem

I have just updated form 2.3 to 2.5 and everything works fine except for one thing..

When I had my 2.3 version installed my blogs homepage was named blog.php and was placed in the root directory with all other files in a directory named blog. It seems that the new version of 2.5 really needs to have the homepage named index.php. All I get now is this message, “Not Found Sorry, but you are looking for something that isn’t here“. This creates problems for the structure of my site.. If I have the blog homepage named index.php I will lose my original homepage, and I don’t want the blog to be the homepage.. Another thing is that I MUST keep the blog address pointed to the root directory..

Is there any ways around this, or am I just out of luck?