Problem with post links

Hello, i have a big problem with my post links, comments, read more links andin some other…
I read a lot of posts but i can’t fix it… 🙁
When i click the post links, i’ll take an 404 page or it will run the index page!

I’m tryin’:
– To change some themes … but nothing.
– To change the permalinks from the “ugly” posts (p=…) to the other permalinks but nothing! The p=… loads me in index page and the others 404 page!
– To create a (writable) .htaccess file in my run dir (with some text who find here…), but nothing!

I’m run in Windows server (Microsoft-IIS/6.0) with PHP 4.3.11 and MySQL 4.0.17.
The site who has problem is oem.gr and the installation dir is oem.gr/Portal.
– I’m also create some index.html to redirects my to installation dir. I’m tryin’ to delete it… to restore it… if the problem is here, but nothing!

Can someone check it and helps me?
Thanks in advance!
Chris.