By 700m I'll assume that you mean the Dell Inspirion 700m laptop.
A stripped down Windows XP SP2 would work just fine. Install Windows XP, download SP2 and all the critical updates. Go to neowin.net and find the uxtheme.dll patcher, and download the theme of your choice from the neowin.net forums.
Currently I'm using Luna Element 4 black compact with compact start menu. It's slick, but retains enough of the classic Windows interface so that it doesn't look like you're running a PC in an annoying neo-art gallery.
Couple that with the Opera Internet Browser http://www.opera.com (It's way faster than Firefox and has dozens of features that firefox and IE have both ripped off poorly in the last few years.), and a free Office distribution such as OpenOffice.org, and you're set.
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