I can not use any seo products...

Everyone's .htaccess is going to be different based on their site, host and server configurations. I use vbSEO over Zoints, but according to this post the original .htaccess is this:

Options +FollowSymlinks
RewriteEngine on
RewriteRule ^([a-z0-9_\-]*-(f|all)[0-9]+(p[0-9]+|/index[0-9]*)?\.html)$ forumdisplay.php/$1 [QSA,L]
RewriteRule ^([a-z0-9_\-]*-(t|p)[0-9]+(p[0-9]+|/index[0-9]*)?\.html)$ showthread.php/$1 [QSA,L]
RewriteCond %{REQUEST_URI} !(index\.php|\.css) [NC]
RewriteRule ^(archive|sitemap)/(.*)$ $1/index.php/$2 [QSA,L]

My honest opinion - if you want an SEO product that works, and you're serious about your forums and aren't keen on this kind of thing, just get vbSEO. It's worth every penny.