There's really no way to revert. You have to reinstall.
To not lose your files, I'd back up the whole hard drive first.
What don't you like about it? Somethings can be changed with third-party software. Classic Shell is very popular, and I use it here. See
http://www.classicshell.net
Personally, I don't care for 7 either. 8 is terrible. But XP doesn't work with my new laptop, and it was 6GB of RAM. I'd lose that if I usede Win XP, as it only see about 3.5GB of the RAM. I'd be downgrading my hardware.
Windows 7 is safer than Windows XP, if you're one of those malware magnets like my parents used to be. They were moved to Xubuntu Linux, and nary a problem since!