changing two column wordpress theme to one column



Remove it from the main loop and all related template files (part you are removing is conveniently called sidebar.php in most themes) and then adjust the width of the main column.

Well, thats the easy solution in a perfect world. Of course smaller tweaks will have to be made to the css and shit to get everything looking right.

Really, just depends on the theme. That being said, what theme is it? lol
 
As above said yes you can remove the sidebar.php call from Index.php
Also u can have plugins to disable the sidebars on page level, may be you could keep it one page and disable it in other page.....Juts google it.
 
Depends on which theme you are using. For example, now a days themes have advanced option panel on WP admin. Most of the premium themes have template attribute options "full width" "one-sidebar" "two-sidebar" "left-sidebar" "right-sidebar" etc. You can easily select the desired from individual page/post. WordPress theme Modernize is one of the best example of them.

If it is a case of modifying theme files, I will suggest to look on sidebar.php file. Some templates have two sidebar files, depends on the template developer how he design. The concept is to remove one sidebar code and fix the other sidebar CSS which you want to keep. A detail information about the theme might help.
 
it's a customised artisteer theme, probably just get a designer to do it, hate doing this shit.
 
Wordpress codex is your best friend. This is extremely easy to do, just depends on the theme. Some have theme options, some will need you to go into the theme files and remove get_sidebar() but of course that could screw up the layout. However, most themes are set up in a way where if you remove that, it should fix layout automagically. You may need to do some CSS adjustments though, like making the left width container a little wider to make up for the lost space. Good luck bros!
 
it's a customised artisteer theme, probably just get a designer to do it, hate doing this shit.

Okay, then I believe it needs to work on theme files as well as cascade style-sheet to resolve this issue. Hiring a designer would better option if you do not have enough time to study Wordpress resources like digga121 said "WordPress codex". Please make sure you choose a good designer and keep website backup before modification. Stay safe.