The idea that Office 2007 is "cluttered" etc. is pretty silly.
It's cluttered and it's poorly designed. The current way most interfaces are designed has prevailed for so many years not just because everyone knows where everything is by now, but because everything is exactly where you would think it would be. File-related tasks are in the "file" menu, help-related tasks are in the "help" menu, and editing tasks are in the "edit" menu. In Office 2007's wonderful interface, file-related tasks are in a picture of the logo, help-related stuff is in a picture of a circle with a "?," and some of the file editing tasks are in "home," while some are in other menus. Microsoft forgot that "if it ain't broke, don't fix it," and ended up messing up something good.
Also, it's a stupid idea to, in a Microsoft Office-established world, suggest that someone do the switch to OpenOffice.org, methinks. Most businesses and education facilities rely on compatibility most times.
OpenOffice has support for every Office format that exists, as well as many other formats, including the ODF format, which is used by many governments and educational institutions (source). Its support for older Office formats is pretty good; it'll even read some files that Office refuses to read and labels "corrupt." Office, on the other hand, has never supported ODF until a few days ago, when Office 2007 SP2 launched with "support" for ODF. I put that in quotes because Office won't read ODF spreadsheets from any other application, and its ODF spreadsheets can only be read by the "CleverAge" plugin, a Microsoft-sponsored Add-in for Office to view ODF (source, source).
I suggest that you wait until Office 2010 comes out, then buy that. Or if you really want Office 2007, go ahead, but it's really complicated. (2010 will be even more complicated, unless Microsoft has learned that not all its customers are techies).
A better idea would just be to use OpenOffice.org or Office XP. Both have the classic interface you're looking for, though Office XP is, AFAIK, no longer supported by MS.