Normally, files preceded by a . are hidden files - have you used any applications that allow you to show hidden files?
.DS_store files contain information about window position, size and view options... icon, column, list etc... They also store OS X file comments.
You can delete them, but they'll just reappear - and every one of your folder windows will return to a default state. Meaning you'll have to repostion them all again to your liking.
Cocktail will allow you to show or hide hidden files - it will also allow you to remove .DS_store files.
Download it here:
http://www.macosxcocktail.com/