order topics by last updated

hello! i am totally stumped...i can find NO solution to my problem. i coded my own forum from scratch because i didn't want to use conventional forum software...everything has been going great...but i have run into a snag. the topics are currently displayed according to the $postTIME in a decending fasion...so newer topics go up top. this is not really how i want it. i can't wrap my brain around how i would display the topics like they are here, topics that are posted are bumped to the top. if anyone can help me i would be GREATLY appriciative!

here is the forum btw: http://flashanims.com/forums/index.php

oh, and also...if someone could point me i the right direction as to how i would display the last user that posted in a said topic/if the topic has been viewed or not.

Thanks alot!

You can't just add a timestamp column that is updated with each new post and use an ORDER `column_name` BY DESC to display the most recent post?

Additionally, you can have a `viewed` column that is updated whenever a post is read....

well the thing is...i have a timestamp column that is already there, and it has the default set to current timestamp and on auto update properties...and it won't let me make a duplicate of that >_>. what i am thinking of, is if i make a text or int column and use the php date function to manually update it with the date.