If I reinstall Windows XP on my machine, will I have to reinstall everything? Does it wipe the hard drive (i.e. all my pictures and documents)?
A simple repair of the operating system won't wipe your pictures and documents but a reformat will and there's a good chance that a reinstallation will want to reformat the drive.
If you do reinstall without formatting you will have reinstall all your applications again. The files will still be on the hard drive in the same locations (maybe not those that get installed under the Windows directory though) but the registry will have been reset so Windows will have "forgotten" all about them.
It's essential to back up all your documents, pictures, music, installation programs etc. before performing anything major like a reinstallation. In fact it's essential that you perform regular backups of your data anyway.
Excuse me while I go and check mine....
You can re-install Windows without formatting the drive which will leave all your files in tact although you will have to reinstall any software that requires registering itself with windows (in the registry).
It is usually better to do a completely clean re-install (ie, format before installing) but if you are trying to repair a windows install in order to retrieve documents then yes, you can install windows and all your documents will still be there (usually in a Windows.Old or Username.Old folder).
I'd recommend backing up as soon as you retrieve your documents so you don't have to worry with this in future :-)
(A quick and easy backup for smaller size backups (ie, documents and photos rather than huge video files) would be something simple like DropBox).
Best way to act would be:
Backup all your important files
Yes, to all the stuff that requires installation (Office, photoshop etc).
No, to all the pictures and documents. You will simply need to find them once you reinstall. This assumes you don't wipe the drive during the re-install. You will have the option of wiping the drive or simply installing another instance.