yes, it's absolutely possible. in fact, all those bits are part of one image that can be extracted and edited very easily using any resource hacker.
Windows 7 can be skinned just like Vista or XP. but it takes a lot of work to do a full custom skin, and most people don't even know about Windows 7 yet. windows visual styles are made up of hundreds of individual images and a massive settings file, and it's a lot of work to edit every one of them.
there is a way to sort of port styles at the moment, from both XP and Vista, but since 7 has new UI elements, it takes a lot of adjusting to get them working just right.
just give it time. in 6 months, DA will be flooded with visual styles for Windows 7