If all your documents and photos are stored in subfolders of the My Documents folder, then it should be enough to backup the My Documents folder.
Personally, I'd backup the complete c:\users\<your_username> folder just in case, though, because it contains a lot more important stuff, like email, bookmarks, program settings etc.
Email and bookmarks are usually very important, so you may want to export them separately in order to be able to quickly re-import them afterwards.
For formatting it should generally suffice to use the installation DVD. But if you want to make absolutely sure everything is erased prior to reinstalling, and if you don't trust the MS tools, then download the Parted Magic live CD (
www.partedmagic.com ), boot of it, and use the partitioning tool to delete all partitions.
