Directories and .htaccess problems

New Poster, long time browser here.

1.
I am currently running Apache Server 2.0.52 with PHP 4.3.9.

What I was wondering was how would I go about making urls
such as http://www.some-site.com/dir1/somepg.html look like
http://www.some-site.com/dir1. (Minus the period obviously)

If anyone could help it would be very much appreciated, and
as always, thanks in advance for any help given.

2.
As you may guess this question has to do with a .htaccess file.

I am running on a Windows 2000 machine. What I want to do is create
a .htaccess file which will have a DirectoryIndex file.php directive in it
and have it work! I have created the file, but when I access the directory
it gives me a HTTP 500 (Internal Server Error) Message instead of displaying
file.php. The absolutly strange part of this whole scenario is that I have a
.htaccess file in my server's root directory which works fine. It seems as though
my .htaccess file in a subdirectory does not work?

Any suggestions?